### Past Seminar

• Title of the talk: "In house lectures on Nobel prize 2020 in medicine, chemistry and Physics"
Speaker: Dr. Sachin Kumar, BSBE, IITG, Dr. B. Anand, BSBE, IITG and Dr. Sayan Chakraboarti, Physics, IITG
Date & Time: 20 November 2020, 05:00 PM
Abstract of the talk:

In house special lectures on Nobel prize 2020 in medicine, chemistry and Physics.

• Title of the talk: "Nonequilibrium Thermodynamics of Open Quantum Systems"
Speaker: Dr. Md Manirul Ali, Former research staff, National center for Theoretical Sciences, Taiwan
Date & Time: 07 October 2020, 04:00 PM
Abstract of the talk:

Thermodynamics is built with the concept of equilibrium states. However, it is less clear how equilibrium thermodynamics emerges through the dynamics that follows the principle of quantum mechanics. In this paper, we develop a theory of quantum thermodynamics that is applicable for arbitrary small systems, even for single particle systems coupled with a reservoir. We generalize the concept of temperature beyond equilibrium that depends on the detailed dynamics of quantum states. We apply the theory to a cavity system and a two‑level system interacting with a reservoir, respectively. The results unravel (1) the emergence of thermodynamics naturally from the exact quantum dynamics in the weak system‑reservoir coupling regime without introducing the hypothesis of equilibrium between the system and the reservoir from the beginning; (2) the emergence of thermodynamics in the intermediate system‑reservoir coupling regime where the Born‑Markovian approximation is broken down; (3) the breakdown of thermodynamics due to the long-time non-Markovian memory effect arising from the occurrence of localized bound states; (4) the existence of dynamical quantum phase transition associated with negative dynamical temperature. The corresponding dynamical criticality provides a border separating classical and quantum world. Third law of thermodynamics, allocated in the deep quantum realm, is naturally proved.

References:
1. Quantum thermodynamics of single particle systems, Md. Manirul Ali, Wei-Ming Huang and Wei-Min Zhang, Scientific Reports 10, 13500 (2020).

• Title of the talk: "Metamaterial based single photon emitters"
Speaker: Prof. Venu Gopal Achanta of TIFR
Date & Time: 05 March 2020, 12:00 noon
Venue: Seminar Room, Department of Physics
Abstract of the talk:

Single photon emitters that can work on demand, that is, emit when triggered are of utmost importance for practical implementation of quantum information processing. For efficient single photon emitters, one would need to optimize the overall efficiency that includes both the quantum efficiency as well as the collection efficiency. Solid-state equivalent of 2-level systems like quantum dots or nanoparticles and colour centres in materials like nanodiamonds, SiC, among others are studied as dipole emitters that are embedded in different hosts. For higher quantum efficiency, manipulation of the photonic local density of states in the host medium is necessary to achieve maximum Purcell factor. Further design would require efficient out-coupling of photons to the far-field which is, typically, air or an optical fiber. In this talk, I will present dipole emitters in photonic crystal microcavity as well as metamaterials to enhance their overall emission efficiency in particular directions..

• Title of the talk: "Berry phase and quantum Hall effect"
Speaker: Prof. Angom D.K. Singh, Physical research laboratory
Date & Time: 27 February 2020, 02:30 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

Quantum Hall effect is the quantization of conductivity in two-dimensional conductors in the presence of an external magnetic field. It occurs in two flavours: the integer quantum Hall effect; and the fractional quantum Hall effect. The former can be understood in terms of non-interacting electron cloud, but the latter requires interactions. The effect arises from the Landau quantization of the electron states in the presence of the external magnetic field. And, quantization of the conductivity is closely related to the Berry phase of the electrons. We shall explore this relation in the presentation.

• Title of the talk: "Next Gen Process Diagnostics in Semiconductor Manufacturing"
Speaker: Sujit Jha, Director, Engineering Management at Applied Materials India
Date & Time: 26 February 2020, 05:15 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

While advanced nodes and newer materials are key to the growth of semiconductor industry, there is only so much that can be achieved by following the Moore’s law. Focus also needs to be shifted towards the expanding applications that the era of IoT & AI have brought along. Wafer fabrication equipment companies need to solve increasingly complex materials driven problems and help to accelerate time-to-market. In order to do that we need to capture massive data and critical info, make it structured, accessible and searchable. We need to develop tools and solutions with innovative usage of sensors and leveraging recent progress in machine learning to generate next generation predictive analytics. In a nut shell, making process equipment smarter and faster with synergistic hardware and computational enhancements. We need to be able to do faster development, qualification & ramp with predictable product performance. We need to be able to predict problems in processes/tools and find solutions even before they become a nuisance for fabs. This is where some of our new initiatives at Applied Materials come into picture. We use existing sensors and apply them to newer innovative usage to capture whatever is happening inside the process tools plasma, chamber walls & wafers. We will present some use cases in which optics and spectroscopy can be used in several innovative ways to improve their applicability and provide immense value to chip making companies.

• Title of the talk: "Observational aspects of Black Hole Binaries"
Speaker: Dr. H. Sreehari, IISC, URSC, ISRO
Date & Time: 18 February 2020, 11:30 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The death of a star due to gravitational collapse results in the formation of astrophysical compact objects like white dwarfs, neutron stars and black holes. We focus our studies on stellar mass black holes that appear in accretion powered X-ray binary (XRB) systems. XRBs are known to produce X-ray outbursts, during which the flux from the source increases above its quiescent state and remain so for a duration of a few weeks to years. Using space based X-ray observatories (RXTE, Swift, NuSTAR, AstroSat and MAXI), we observe black hole XRBs (XTE J1859+226, GX 339-4, IGR J17091-3624, GRS 1915+105 & MAXI J1535-571) and model the temporal and spectral data to understand the physical processes that lead to the emission from the sources. We modelled the Quasi-periodic Oscillation (QPO) features in the power spectra of BHBs and their time evolution was explained with the propagation of shocks in the accretion flow. Further, we modelled the broadband energy spectra (0.5 – 150 keV) to understand source characteristics (eg: state transitions, flux contribution from disc and corona) using phenomenological models and estimated accretion parameters like accretion rates and size of compton corona (shock radius) using the two-component accretion flow model. Following this, we used three indirect methods to estimate the mass range of black holes (GX 339-4, IGR J17091-3624) whose mass cannot be estimated dynamically. Following this, I will present the properties of one of the most recently discovered BHB (MAXI J1535-571) and the characteristics of high frequency QPOs in the source GRS 1915+105 using observations from India’s first multi-wavelength astronomy satellite (AstroSat). Finally, I will discuss machine learning techniques for spectral state classification.

• Title of the talk: "Lecture series on Theoretical Physics"
Speaker: Prof. N. D. Haridass (formerly of IMSc, Chennai)
Date & Time: 10 - 14 February 2020, 05:15 pm
Venue: CET e-classroom

• Title of the talk: "Cavity quantum electrodynamics using semiconductors"
Speaker: Prof. P. K. Pathak, School of Basic Sciences, IIT Mandi, Himachal Pradesh
Date & Time: 06 February 2020, 05:00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

In the quest for realization of scalable on-chip quantum technology, semiconductor quantum dots (QDs) have emerged as a potential candidate. With the advanced lithography techniques it is possible now to grow a quantum dot at desired location inside a photonic crystal microcavity. As a result, new solid state on-chip cavity quantum electrodynamics (cavity-QED) systems have been developed. In this seminar I will discuss proposals for generating entangled photon sources, two-photon sources, microlasers and phonon assisted two-photon resonant interactions.

• Title of the talk: "Hyperspectral Imaging - A Unique Combination for Multipurpose Application"
Speaker: Dipankar Das, Co-founders of Spectral Insights Pvt Ltd
Date & Time: 30 January 2020, 05:15 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The Hyperspectral imaging used for the first time by NASA for remote sensing application originates by combing two most powerful subjects; Imaging Science and Spectroscopy. Whereas the human eye visualize objects over a narrow band of the electromagnetic spectrum (400 – 700nm); Hyperspectral imaging device could record images with high spatial and spectral resolution over a broad range of the electromagnetic spectrum. This fusion of spatial and spectral information opens a new avenue for analysis, and a unique opportunity for processing and understanding characteristics of an image scene. The goal of hyperspectral imaging is to obtain the spectrum for each pixel in the image of a scene, with the purpose of finding objects, identifying materials, or detecting processes.

Today, hyperspectral imaging systems are available for applications in astronomy, agriculture, biomedical imaging, geosciences, physics, and surveillance. In this presentation I will describe few application areas (mainly application of Hyperspectral Imaging in digital pathology) we are working in past few years and pathways to make cost-effective hyperspectral imaging solution to different fields.

Furthermore, I will discuss the journey of an Entrepreneurship to bring this technology to a viable product in Healthcare Industry.

• Title of the talk: "Inflationary Universe in F(R) Gravity with Asymmetric tensor fields and their suppression during its evolution"
Speaker: Dr. Tanmoy Paul, Chandernagor College, West Bengal
Date & Time: 29 January 2020, 05:15 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The intriguing question, why the present scale of the universe is free from any perceptible footprints of rank-2 antisymmetric tensor fields (generally known as Kalb-Ramond fields), is addressed. A quite natural explanation of this issue is given from the angle of higher-curvature gravity, both in four- and in five-dimensional spacetime. The results here obtained reveal that the amplitude of the Kalb-Ramond field may be actually large and play a significant role during the early universe, while the presence of higher-order gravity suppresses this field during the cosmological evolution, so that it eventually becomes negligible in the current universe. Besides the suppression of the Kalb-Ramond field, the extra degree of freedom in F(R) gravity, usually known as scalaron, also turns out to be responsible for inflation. Such F(R) gravity with Kalb-Ramond fields may govern the early universe to undergo an inflationary stage at early times (with the subsequent graceful exit) for a wider range of F(R) gravity than without antisymmetric fields. Furthermore, the models—in four- and five-dimensional spacetimes—are linked to observational constraints, with the conclusion that the corresponding values of the spectral index and tensor-to-scalar ratio closely match the values provided by the Planck survey 2018 data.

• Title of the talk: "Astrophysical Black Holes: A Review"
Speaker: Prof. Cosimo Bambi, Fudan University, China
Date & Time: 20 January 2020, 05:15 pm
Venue: Seminar Room, Department of Physics

• Title of the talk: "Fermilab Muon g-2 Experiment: A Magnetic Moment in History"
Speaker: Dr. Atanu Nath, INFN - Istituto Nazionale Di Fisica Nucleare - sezione di Napoli
Date & Time: 10 January 2020, 05:00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The Muon g-2 experiment at Fermilab (E989) is currently measuring the muon magnetic anomaly with a goal precision of 140 parts per billion, which will be a fourfold precision improvement over the current best measurement by the previous muon g-2 experiment at the Brookhaven Laboratory (BNL). The BNL-measured value of the muon magnetic anomaly and the corresponding Standard Model (SM) best estimate, differ by more than three standard deviation which inspired the current measurement as well as a theoretical drive for a significantly more precise calculation of the muon magnetic anomaly to rule out (or establish) statistical fluctuation as the origin of such a huge discrepancy. Stable central values along with 4-fold precision improvements in both theoretical (SM) and experimental fronts, would imply a ~ 7σ discrepancy and that will be a clear hint of the physics beyond the Standard Model. Such unprecedented precision demands state-of-the-art technological improvements in all involved components to keep the systematic uncertainty below 70 ppb. This paper reports the current status of the E989 experiment after two years of data acquisition.

• Title of the talk: "X-ray Relativistic Reflection & Testing Strong Gravity"
Speaker: Dr. Kishalay Choudhury, IUCAA
Date & Time: 09 January 2020, 05:15 pm
Venue: Seminar Room, Department of Physics

• Title of the talk: "Baryon Number Violating Nucleon and Dinucleon Decays"
Speaker: Sudhakantha Girmohanta, Stony Brook University, USA
Date & Time: 07 January 2020, 03:30 pm
Venue: Seminar Room, Department of Physics

• Title of the talk: "Seeing is Believing: Experimental Insights about Supercooled Liquids, Glasses and Controlled Crystallization"
Speaker: Dr. Chandan K Mishra, University of Pennsylvania
Date & Time: 06 January 2020, 11:00 am
Venue: Conference Room, Department of Physics

• Title of the talk: "Spectroscopic Ellipsometry of Metal Oxide thin films"
Speaker: Prof Shyama Rath, Department of Physics and Astrophysics, University of Delhi
Date & Time: 18 December 2019, 11:00 am
Venue: Seminar room, Department of Physics
Abstract of the talk:

• Title of the talk: "Two-Higgs-Doublet-Model and Muon g-2"
Speaker: Prof. E. J. Chun, Korean Institute for Advanced Studies (KIAS)
Date & Time: 12 December 2019, 04:00 pm
Venue: Conference Room, Department of Physics
Abstract of the talk:

Among various types of two-Higgs-doublet models, the type-X model is known to accommodate the muon g-2 anomaly. We will discuss various features of the model in relation to muon g-2 and the prospect of testing them in future collider experiments.

• Title of the talk: "Gate-Tunable Flatbands in Graphene Moiré Superlattices"
Speaker: Dr. Bheema Linagm Chittari, Univ. of Seoul
Date & Time: 09 December 2019, 04:00 pm
Venue: Conference Room, Department of Physics

• Title of the talk: "Tensor network description of quantum many-body systems: applications to real materials and quantum simulators"
Speaker: Prof. Augustine Kshetrimayum, University of Berlin
Date & Time: 02 December 2019, 04:00 pm
Venue: Seminar room, Department of Physics
Abstract of the talk:

Due to the exponential growth of the dimensions of the Hilbert space with the number of particles, quantum many-body problems continue to be one of the greatest challenges in physics. In this talk, I will give an introduction to Tensor network techniques which can be used to study challenging quantum many-body problems. In particular, I will talk about some of our recent works in the group where we employ these techniques to study an actual quantum magnet Ca10Cr7O28, recently discovered to have properties of a quantum spin liquid. I will then talk about an annealing algorithm based on tensor networks for 2D finite temperature states. I will also show how they can be used as a benchmarking and guiding tool for experiments involving cold atoms.

References:
1. A Kshetrimayum, C Balz, B Lake, J Eisert arXiv:1904.00028 (2019)
2. A Kshetrimayum, M Rizzi, J Eisert, R Orús PRL 122 (7), 070502 (2019)
3. A Kshetrimayum, H Weimer, R Orús Nature communications 8 (1), 1291 (2017)

• Title of the talk: "Exploring Dark-ALP portals at future e+e- colliders"
Speaker: Dr. Sanjoy Biswas, RKMVERI, Belur
Date & Time: 29 November 2019, 05:00 pm
Venue: Conference Room, Department of Physics
Abstract of the talk:

In this talk, I will discuss the searches for Axion-Like-Particles (ALP) at future e+ e- colliders. In particular, I will discuss the collider phenomenology of ALP-photon-photon and ALP-photon-dark photon couplings in the context of the future e+ e- colliders. I will illustrate that these interactions can be efficiently probed at future e+ e- colliders in the di-photon+missing energy channel, where the missing energy has the origin in the invisible dark photon in the final state. The di-photon+missing energy channel turns out to be more sensitive probe of the ALP than the traditional tri-photon channel.

• Title of the talk: "What if photon has a mass?"
Speaker: Prof. T. R. Govindarajan, Institute of Mathematical sciences
Date & Time: 08 November 2019, 05:15 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

Schrodinger queried 50 years back what will happen if photon had a small mass. He answered that Electrodynamics both classical and quantum will acquire only small corrections. He used this to establish a bound on the mass of photon which is valid even now, except for some improvements in experimental accuracies. We revisit this question from new perspective of asymptotic symmetries, cosmology and dark matter. It rekindles old questions on the nature of vacuum and aether!! Be prepared for surprises!!

• Title of the talk: "Murray Gell-Mann -- A Brief Introduction to his Life and Work"
Speaker: Prof. B. Ananthnarayan, IISC Bangalore
Date & Time: 04 November 2019, 05:00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

Murray Gell-Mann who recently passed away was a tremendously influential physicist best known for his contributions to elementary particle physics, especially to quantum field theory, and the strong interactions. His repertoire was far larger. In this talk we will recall some of the features of his extraordinary life and work and say a few words about his ideas beyond elementary particle physics.

• Title of the talk: "Satyendra Nath Bose and the development of Quantum mechanics"
Speaker: Prof. Rabin Banerjee, S. N. Bose National Center for Basic Sciences, Kolkata
Date & Time: 01 November 2019, 05:15 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

In the year 1924, in a couple of papers from Dhaka University, S.N. Bose gave a radically new derivation of the black body radiation law. Abraham Pais, in his scientific biography of Albert Eisntein, remarked that this work is the last of the four fundamental papers in old quantum theory, the other three being by Planck, Einstein and Bohr. Bose introduced the concept of indistinguishability in physics which was the big idea that shaped the subsequent development of quantum mechanics, eventually leading to quantum field theory. We give a pedagogical presentation of this development, primarily aimed at the students.

• Title of the talk: "Ultrafast Laser Produced Plasmas: Generation, Characterization and Applications"
Speaker: Prof. Reji Philip, Raman Research Institute, Bangalore
Date & Time: 01 November 2019, 11:00 am
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The field of laser-produced plasmas (LPP) has greatly attracted the research community because of its wide range of applications, which include pulsed laser deposition, generation of X-rays and ion beams, plasma based acceleration etc. This talk will open with a general introduction to plasmas (ultrafast LPPs in particular), followed by a discussion of the general plasma diagnostic methods (optical and electrical). Experimental determination of plasma density and temperature will be discussed, and the spectral and temporal characterization of LPPs generated in metallic targets will be elaborated. X-ray emission from LPPs of noble metal nanoparticle suspensions will be discussed. Some applications including High Harmonic Generation (HHG) will be outlined.

• Title of the talk: "Contribution of Michel Mayor and Didier Queloz to Discovery of Exoplanets"
Speaker: Dr. Santabrata Das, IIT Guwahati
Date & Time: 29 October 2019, 05:45 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

• Title of the talk: "Contribution of James Peebles to Physical Cosmology"
Speaker: Dr. Debaprasad Maity, IIT Guwahati
Date & Time: 29 October 2019, 05:15 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

• Title of the talk: "Dielectrics and ferroelectrics for microwave applications"
Speaker: Prof. K. C. James Raju, University of Hyderabad
Date & Time: 10 October 2019, 11:30 am
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The present era is characterized by the dominance of mobile communications and the range of applications that provides. They work in the microwave frequency range and hence why microwaves are being used for such applications will be reviewed. As the demand for mobile communication increases, demand for new devices also increases. Not only it places new demands on design, but also new materials and phenomena are being pressed into service. For example, materials with high dielectric constant, low dielectric loss and temperature independent properties are used for making microwave dielectric resonators (DRs) while using electromechanical resonances exhibited by ferroelectric thin films, miniature resonators like film bulk acoustic resonators (FBAR) and related high overtone resonators (HBARs) are being developed for 5G applications. High Q resonators are useful both in communication as well as in sensors. In addition, efforts are being made to achieve these devices on flexible, polymer and biocompatible substrates. Ferroelectric materials exhibit a voltage dependent dielectric constant and that can be used for realizing varactors using thin films in a relatively simple technology. Using such varactors, it is possible to develop filters, phase shifters and tunable impedance matching networks which are voltage tunable. At smaller voltages, they can be tuned using less than 5 volts and hence can be tuned using digital circuits paving the way for a means for realizing software defined radios. These films are being made for such applications using RF sputtering and Pulsed Laser Deposition. In this talk, these topics and related activities that are being pursued at University of Hyderabad will be presented.

• Title of the talk: "Minimal Sub-GeV Dark Matter Scenarios"
Speaker: Dr. Soumya Rao, Former postdoc at National Centre for Nuclear Research, Poland
Date & Time: 26 September 2019, 05.00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

Thermal dark matter scenarios based on light (sub-GeV) fermions typically require the presence of an extra dark sector containing both a massive dark photon along with a dark Higgs boson. The latter typically generates both the dark photon mass and an additional mass term for the dark sector fermions. We study the phenomenology and experimental constraints on two minimal, self-consistent dark sectors that include such a light dark Higgs boson. In one the dark matter is a pseudo-Dirac fermion, in the other a complex scalar. We find that the constraints from BBN and CMB are considerably relaxed in the framework of such minimal dark sectors. We present detection prospects for the dark Higgs boson in existing and projected proton beam-dump experiments. We emphasize in particular the effect of the dark Higgs boson on both detection prospects and cosmological bounds. We point out that in addition to the well studied pseudo-Dirac regime, this model can achieve the correct relic density in three different scenarios, and examine in details their properties and experimental prospects. We show that future searches at experiments like Xenon1T or LDMX can probe all the relevant parameter space, complementing the various upcoming indirect constraints from astrophysical observations.

• Title of the talk: "The study of disk structures around the black holes"
Speaker: Dr. Rajiv Kumar, ARIES, Nainital
Date & Time: 26 September 2019, 03.00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

In this talk I will discuss two things; one is about two-dimensional disk structures and second, self- similar solutions for the finite size of the disk around the black hole. We have solved steady-state, axisymmetric viscous 2D fluid equations of motion for accretion and outflows in spherical polar coordinates (r, θ, φ). First time in the analytical study, we have used two azimuthal components of the viscous stress tensors namely, τ_{rφ} and τ_{θφ}. We found supersonic and subsonic regions in the inflow region and the outflows occurred in the subsonic inflow region above the equatorial plane. We also found that the structure and size of the 2D disk are affected by the viscosity and the ADAF size of the disk. We also explored the outflows, no outflows, and failed outflows solutions around the BH. Second part I will talk about the hybrid disk geometry and implications of hybrid disk and self-similar solutions.

• Title of the talk: "Higgs boson at the age of seven: What we know and what may lie ahead"
Speaker: Prof. Poulose Poulose, IIT Guwahati
Date & Time: 12 September 2019, 05:15 pm
Venue: Seminar Room, Department of Physics

• Title of the talk: "Recent Developments in μ - τ Symmetry"
Speaker: Dr. Newton Nath, IHEP, Beijing
Date & Time: 02 September 2019, 05.00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

Symmetry-based studies have been very successful to explain the observed mixing pattern of neutrinos. Among number of such approaches, \mu-\tau reflection symmetry, which predicts θ_{23}=Π/4, δ=\pm Π/2 together with non-zero θ_{13}, attracts a lot of attention in recent times. On the other hand, the type-I seesaw mechanism remains the simplest and elegant one to describe the theory behind the neutrino mass. In this talk, we shall discuss the μ - τ reflection symmetry which we embed into the minimal seesaw model to explain both the neutrino mass and mixings. Furthermore, to explain the latest global best-fit values of neutrino oscillation data, which favor non-maximal values of θ_{23} and δ, we shall talk about the breaking of such symmetry. We shall also talk about the generalize CP-symmetry and bi-large ansatze to explain the leptonic mixing patterns. Finally, we shall discuss the consequences of such symmetry for the long baseline neutrino oscillation experiment, DUNE as well as neutrinoless double beta decay experiments.

• Title of the talk: "Semi-Dirac Materials: Their directional dependent optical conductivity and optimal power/efficiency as a quantum thermoelectrics"
Speaker: Dr. Alestin Mawrie, IIT Bombay
Date & Time: 27 August 2019, 05.00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

There will be two sections in the talk that will consist of the study of optical conductivity and thermoelectricity based on semi-Dirac materials.

In the first section, we show that the gap parameter in semi-Dirac material induces a large degree of sensitivity for interband optical conductivity with respect to the polarization direction. The optical conductivity reveals an abruptly large value at a certain frequency for light along a particular polarization direction while it is significantly suppressed along the direction orthogonal to the former. The direction-dependent optical conductivity may, in turn, be used to uniquely predict the dispersive nature of the two-dimensional semi-Dirac materials, in addition to other possible applications in the field of transparent conductors.

In the second section of the talk, we give a prediction that the gap parameter manifests itself by enhancing the thermoelectric figure of merit $zT$ as the chemical potential crosses the gap, followed by a sign change in the Seebeck coefficient around the same point. Subsequently, whenever the chemical potential crosses the gap potential parameter, there is a well-balanced maximum of the power factor and the efficiency of the thermoelectrics. An optimal operating point where co-maximization of the power efficiency occurs is consequently singled out for the best thermoelectric performance. This section of our work will pave the way for the use of two-dimensional semi-Dirac materials for thermoelectric applications.

References:
1. A. Mawrie and B. Muralidharan, Physical Review B 100, 081403(R) (2019).
2. A. Mawrie and B. Muralidharan, Physical Review B 99, 075415 (2019).

• Title of the talk: "Gravitational collapse and baby universe"
Speaker: Hrishikesh Chakrabarty, Graduate student, Fudan University, Shanghai
Date & Time: 21 August 2019, 05.00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

We present a dynamical toy model for an expanding universe inside a black hole. The purpose of the model is to suggest a possible reconciliation between the observation that black holes are well described by the classical solutions and the fact that the theoretical resolution of space-time singularities leads to a bounce for the collapsing matter.

• Title of the talk: "Majorana nanowire with unconventional superconductivity and RKKY interaction in Borophene"
Speaker: Ganesh C. Paul, Institute of Physics (IOP), Bhubaneswar
Date & Time: 20 August, 05:00 pm
Venue: Seminar Room, Department of Physics

• Title of the talk: "First Principles Study of Skyrmion Formation at 3d/4d Transition Metal Interfaces"
Speaker: Dr. Soumyajyoti Haldar, University of Kiel, Germany
Date & Time: 31 July 2019, 05:00 pm
Venue: Seminar Room, Department of Physics

• Title of the talk: "Gravity safe electroweak natural axionic solution to strong CP and SUSY μ problem in the LHC era with determination of the PQ scale"
Speaker: Dibyashree Sengupta, Oklahoma University, USA
Date & Time: 22 July 2019, 04:30 pm
Venue: Seminar Room, Department of Physics

• Title of the talk: "Black Hole Images: Past, Present, and Future Aspects"
Speaker: Dr. Arka Chatterjee, S. N. Bose National Centre for Basic Sciences, Kolkata
Date & Time: 03 July 2019, 05:00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

Images of Black Hole at the centre of Galaxy Messier 87 has recently shown to us by the Event Horizon Telescope (EHT) collaboration. For the first time, this observation leads us to directly discern the accreting matter from the shadow of the supermassive black hole. Theoretical foundations of black hole images started early 1970’s. The first image of a Keplerian disk rotating around a Schwarzschild black hole was presented by J. P Luminet. Our knowledge of accretion disks has evolved since that time. And, so does the images. One key factor to these images is the gravitational bending of photons around the black holes. In this present talk, I would like to discuss how the initial images were made, what are the current situations and major future challenges that one should overcome to capture the images of stellar mass black holes.

• Title of the talk: "The dipole anisotropy in large scale structures"
Speaker: Prof. Pankaj Jain, IIT Kanpur
Date & Time: 17 June 2019, 11:00 am
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The large scale structures are expected to show a small dipole anisotropy in number counts as well as sky brightness due to our motion with respect to the cosmic frame of rest. The dipole arises due to the Doppler and aberration effect. We obtain a precise relationship between the dipole and the local velocity. For consistency the extracted velocity should agree with that obtained from CMB observations. Using the NVSS data, we find that the direction is in good agreement with the CMB dipole, however the amplitude is much larger, leading to a discrepancy of more than two sigmas. We also apply our formalism to the TGSS data. In this case we find a much larger dipole and also find significant higher multipoles, whose interpretation is unclear. We also discuss the potential of SKA to resolve this issue.

• Title of the talk: "Sensitivity of TeV scale new physics on the electroweak metastability"
Speaker: Dr. Najimuddin Khan, IISC Bangalore
Date & Time: 20 May 2019, 04:00 pm
Venue: Seminar Room, Department of Physics

• Title of the talk: "The ubiquitous Raychaudhuri equations"
Speaker: Prof. Sayan Kar, IIT Kharagpur
Date & Time: 14 May, 2019, 05.00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The Raychaudhuri equations and its consequences will first be introduced using simple examples from mechanics and other areas of physics. Thereafter, we move on to a quick derivation of the equations for the kinematic variables (expansion, shear, rotation) describing the evolution of geodesic congruences in Riemannian and pseudo-Riemannian geometries. Subsequently, the focusing theorem will be presented and its role in the context of the singularity theorems highlighted briefly. We end with a summary of the applications of the Raychaudhuri equations in diverse contexts (including some recent results), thereby emphasizing its ubiquitous nature.

• Title of the talk: "Low Energy Lepton-Proton Scattering - An EFT Approach"
Speaker: Dr. Vanamali Shastry, guest faculty in University of Mangalore, Karnataka
Date & Time: 30 April, 2019, 10.00 am
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The structure of hadrons is an important problem that has far-reaching consequences. The lepton-proton scattering experiments are aimed at studying the structure of the protons. But, the experiments are less accurate in the low energy regime because of the difficulties involving the soft bremsstrahlung photons. This leads to a poor understanding of the low energy structure of hadrons. Heavy Baryon Chiral Perturbation Theory (HBChPT) is a systematic expansion of the chirally invariant Lagrangian in the low-energy regime with baryons as fundamental degrees of freedom. Thus, HBChPT forms a convenient tool to study the lepton-proton scattering process. In this talk, I will discuss our recent efforts to study low energy lepton-proton scattering using HBChPT.

• Title of the talk: "Investigation of magnetized accretion flow properties around a black hole and prospects with Astrosat"
Speaker: Dr. Biplob Sarkar, The ICFAI University, Tripura
Date & Time: 22 April 2019, 04:00 pm
Venue: Seminar Room, Department of Physics

• Title of the talk: "Likely lurking lights?"
Date & Time: 05 April 2019, 04:00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The possibility of light scalars evading our notice for example, in two Higgs doublet scenarios will be discussed, along with some of their implications.

• Title of the talk: "The quantum fate of black hole horizons"
Speaker: Dr. Debajyoti Sarkar, Albert Einstein Center (AEC) for Fundamental Physics, UniversitÃ¤t Bern
Date & Time: 26 Feb 2019, 04:30 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

I will discuss the possibility that in the semi-classical gravitational theory the black hole horizon is non-perturbatively replaced by a wormhole, whose parameters make it a perfect mimicker of a classical black hole. Based on work with Clément Berthiere and Sergey Solodukhin (PLB 786 (2018), 21-27; arXiv 1712.09914 [hep-th]).

• Title of the talk: "Ab initio design strategies for functional materials: Role of temperature-dependent excitations"
Speaker: Dr. Biswanath Dutta, Post Doc at Delft University of Technology
Date & Time: 19 Feb 2019, 05:15 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

• Title of the talk: "Hydrogen-carbide interactions in steels: Ab-initio combined with experiment"
Speaker: Dr. Poulumi Dey, Assistant Professor at Delft University of Technology
Date & Time: 19 Feb 2019, 04:00 pm
Venue: Seminar Room, Department of Physics

• Title of the talk: "Emergent Phenomena in Quantum Materialsâ€‹"
Speaker: Dr. Sreementa Mitra, Post Doc at IISc Bangalore
Date & Time: 18 Feb 2019, 05:20 pm
Venue: Seminar Room, Department of Physics

• Title of the talk: "Status of neutrino mass-mixing parameters"
Speaker: Dr. Francesco Capozzi, Max Planck for Physics, Munich, Germany
Date & Time: 06 Feb, 2019, 04.00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

• Title of the talk: "What does the future bring? A look at high temperature superconducting technology for commercial applications in near future"
Speaker: Dr. Devendra K Namburi, Cambridge University
Date & Time: 07 Jan, 2019, 03.00 pm
Venue: Seminar Room, Department of Physics

• Title of the talk: "Emergence of Complex Topology in Oxide Heterostructure"
Speaker: Dr. Sujit Das, Department of Materials Science & Engineering, University of California, Berkeley, CA 94720, USA
Date & Time: 17 Jan, 2019, 04.00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

Complex topological configurations are a fertile arena to explore novel emergent phenomena and exotic phases in condensed-matter physics. For example, the recent discovery of polarization vortices and the associated complex-phase coexistence and response under applied fields in superlattices of (PbTiO3)n/(SrTiO3)n suggests the presence of a complex, multi-dimensional system capable of exotic physical responses1,2,3,4. Here, by varying epitaxial constraints we report the discovery of room-temperature polar skyrmions in a lead-titanate layer confined by strontium-titanate layers, imaged by atomic-resolution scanning transmission electron microscopy5. Phase-field modeling and second-principles calculations reveal that the polar skyrmions have a skyrmion number of +1, and resonant soft X-ray diffraction experiments show circular dichroism confirming chirality. Such nanometer-scale polar skyrmions are the electric analogs of magnetic skyrmions, and could advance ferroelectrics towards new levels of functionality. Also, it has been observed the negative capacitance region in this nanometer scale objects6,7 and phenomenon could be controlled by electric field and temperature. Such phenomena could advance ferroelectrics towards new levels of functionality.

• Title of the talk: "Optical Tweezer Phonon Laser"
Speaker: Prof. Mishkatul Bhattacharya, Center for Coherence and Quantum Optics, University of Rochester, Rochester, New York 14627, USA
Date & Time: 04 Jan, 2019, 04.00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

We theoretically propose and experimentally realize a phonon laser using an optically levitated nanoparticle. In our system, mechanical gain and nonlinearity are supplied optically. We present theoretical evidence for stimulated emission of phonons, and experimental observations of i) threshold behavior as a function of gain, ii) the transition in phonon statistics from Boltzmann to Poisson across the threshold, and iii) subthermal phonon number squeezing far above threshold. The experimental data agrees well with our microscopic quantum mechanical theory. Our work represents a substantial advance in the generation of coherent phonons in levitated systems and can be readily extended to other physical platforms.

• Title of the talk: "First-principle study of thermal conductivity of DX centers in GaAs"
Speaker: Dr. Ashish Kundu, Projectass, TU Wien, Vienna, Austria
Date & Time: 03 Jan, 2019, 10.00 am
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The lattice thermal conductivity is a dominant mechanism over a wide range of carrier concentrations in several III-V semiconductors. The manipulation and control of the lattice thermal conductivity have impacted an enormous variety of technical applications. We study the influence of DX centers (deep-level defect) formed by SAs, SeAs and TeAs impurities in GaAs, on the lattice thermal conductivity from first principles. We find that DX centers lead to a substantial reduction of the lattice thermal conductivity for all considered impurities. This reduction is due to enhanced phonon scattering rates caused by the lattice distortion. Further decrease of thermal conductivity is found for few DX centers due to resonance phonon scattering.

• Title of the talk: "E(6) inspired U(1)' extension of MSSM: from Dark Matter to LHC"
Speaker: Prof. Mariana Frank, Concordia University, Montreal, Canada
Date & Time: 11 December, 2018, 04.30 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

I review briefly the motivation for supersymmetry, and for extending the gauge symmetry by an extra U(1), consistent with symmetry breaking from E6 SUSY GUT. Imposing universality conditions from the GUT scale, and using experimental constraints, I perform a scan of the parameters of the model. Both the right-handed sneutrino and the lightest neutralino can serve as DM candidates. Constraints from cosmic abundance and direct detection restrict the parameter space in each case. Finally, I discuss the possibility of observing signals of such models at the LHC. In particular, chargino pair production leading to 2 leptons and missing energy can yield significant signal to background enhancements.

• Title of the talk: "Effective Field Theory -- Why and How ?"
Speaker: Dr. Joydeep Chakrabortty, Associate Professor, Department of Physics, IIT Kanpur
Date & Time: 22 December, 2018, 11.00 am
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The present era of particle physics is a "Curious case of Beyond the Standard Model (BSM) physics". Effective Field Theory (EFT) could be pragmatic approach to understand BSM, if any. But EFT is more than that. It can be used as a field theoretic tool to understand physics of different scales. In this talk I will try to explain how one can use the the EFT as a tool to bridge the physics of different scales in the language of functional methods. In this context I will talk about the working principle of our EFT code "CoDEx". I will also discuss the future directions of the formal aspects of EFT that we are interested in.

• Title of the talk: "Lattice matrix elements for new physics searches"
Speaker: Prof. Amarjit Soni, Brookhaven National Lab, USA
Date & Time: 03 December, 2018, 10.00 am
Venue: Seminar Room, Department of Physics
Abstract of the talk:

It is an integral fact that QCD is an integral part of the Standard Model as well as any of its extensions. But in the low energy sector it is highly non-perturbative. The only rigorous method to treat such a theory is the lattice. In this talk, after a very brief introduction of this method, several applications specifically designed to search for new physics will be discussed.

• Title of the talk: "Light for Information Security"
Speaker: Dr. Naveen K Nishchal, IIT Patna
Date & Time: 26 November, 2018, 03.00 pm
Venue: Seminar Room, Department of Physics, Organised by SPIE IITG Studnet Chapter
Abstract of the talk:

• Title of the talk: "Using Cosmic Microwave Background Radiation to probe the Universe"
Speaker: Prof. T R Seshadri, University of Delhi
Date & Time: 19 November, 2018, 05.00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

• Title of the talk: "Resonating Group Method - Overview and Applications"
Speaker: Dr. Vanamali C. Shastry
Date & Time: 14 November, 2018, 05.00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

Resonating Group Method (RGM) is a technique used to study many-body systems. Since its formulation in 1937, such a methodology has been state-of-the-art in studies relating to clustering phenomena in the light nuclei. It has also been extensively used in studying condensed matter systems. In this talk, I plan to discuss the formal aspects of RGM and its applications to nuclear physics.

• Title of the talk: "Dark Matter: The Particle Perspective"
Date & Time: 31st October, 2018, 05.15 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

• Title of the talk: "Understanding the nature of the interstellar dust and organics: A combined approach"
Speaker: Dr. Isaki SAKON, The University of Tokyo
Date & Time: 30th October, 2018, 11.30 am
Venue: Seminar Room, Department of Physics
Abstract of the talk:

• Title of the talk: "An overview of C-MET's R&D activities and Rare Earth based ceramics and composites for microwave circuit applications"
Speaker: Dr. Dr. N.R. Munirathnam, Director General, Centre for Materials for Electronics Technology, (C-MET: R&D laboratory under Ministry of Electronics and Information Technology (MeitY), Govt. of India)
Date & Time: 22nd October, 2018, 04.00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

C-MET a scientific R&D laboratory under Ministry of Electronics & IT is working on requirement driven R&D in the fields of Microwave substrates, sensors and actuators, Supercapacitors, purification of metals, wide bandgap compound semiconductors, recycling of electronic waste in environmental friendly manner, extraction of refractory metal like hafnium at pilot plant scale, antennas for NavIC, Li-ion batteries and LTCC packaging. Broadly the areas of R&D status are covered.

Microwave dielectric materials gained immense importance in wireless applications and many of the high dielectric ceramics are composed of rare earth elements as one of the constituents which in turn help in fine tuning the end properties by judiciously substituting rare earth ions having varying ionic radii. The personal communication devices and other wireless technology industries, such as direct broadcasting, global positioning systems, mobile communication systems etc. have witnessed an explosive and unprecedented growth in applications. The application areas are fast ranging from simple dielectric resonator to complex 3D modules realized through Low Temperature Co-fired Technology. More recently, rare earths based Ultra Low Temperature Co-fired Ceramics (ULTCC) are also finding applications in realizing miniaturised and cost effective devices including Substrate Integrated Waveguide (SIW) circuits. In order to meet these stringent requirements, novel materials with high dielectric constant and low loss tangent are required. High dielectric constant reduces the circuit size since the wavelength travelling through the medium is inversely proportional to the square root of the dielectric constant. On the other hand, extremely low loss tangent improves the signal integrity and avoids cross talks. Cu-cladded rare earth ceramic filled PTFE planar laminates are the ideal choice for high end microwave circuit fabrication which are currently available only from imported sources. Understanding the need for indigenous technology, C-MET has developed a proprietary and patented process methodology comprising of Sigma Mixing, Extrusion, Calendering followed by Hot pressing (SMECH Process) to fabricate dimensionally stable planar and isotropic PTFE/ceramic composite laminates. Pore free and dimensionally stable planar laminates have been prepared by incorporating variety of rare earth titanate ceramics in the PTFE matrix through SMECH process. C-MET has successfully developed wide variety of filled PTFE substrates with dielectric constant ranging from 2.2 to 14.8 together with ultra-low loss tangent ( 0.0018 at 10 GHz) and the technology for the same is already transferred to Industry for commercial production. High power solid state amplifiers have been fabricated by Raja Ramanna Centre for Advanced Technology (RRCAT), Department of Atomic Energy, Indore operating at a centre frequency of 505.8 MHz, which can withstand output power up to 750 kW. Excellent RF performance was obtained in terms of output power, gain and efficiency during system level evaluation and accordingly the high power solid state amplifiers have been successfully deployed in INDUS-2 particle accelerator.

• Title of the talk: "Nano-fabrication and measurement on Superconducting Quantum Circuit Elements"
Speaker: Dr. Dibyendu Hazra, Aalto University, Finland
Date & Time: 11th October, 2018, 11.00 am
Venue: Seminar Room, Department of Physics
Abstract of the talk:

Superconducting Quantum Circuit elements, the Josephson junctions, in particular, play a pivotal role in the diverse field, like, nano-scale magnetometry and quantum computation using superconducting circuits. In this talk, I shall describe the nano-fabrication and measurements of different types of superconducting quantum circuit elements, particularly, the different avatar of Josephson junctions and superconducting resonators. The detailed nano-fabrication processes, which involved electron beam and photolithography, reactive ion etching, thin film evaporation, to mention only a few, will be spelled out. In this regard, I shall describe a thermal model to explain the origin of hysteresis in nano-bridge quasi-Josephson element and explain how the model, followed by experimental findings, would help us unearthing new phenomena and optimizing device design. I shall, then, present our experimental results on high-impedance kinetic-inductance resonators, quantum-noise-limited microwave amplifier, and microwave single-photon-detector. Finally, I shall touch upon our recent unpublished result on nano-bolometer with record-breaking low noise equivalent power.

• Title of the talk: "Enhancing quantum correlations in optomechanical systems"
Date & Time: 9th October, 2018, 5.00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

In this talk, we will talk about our theoretical study on the quantum correlations present in an optomechanical system. Under experimentally achievable conditions, we will demonstrate that a significant enhancement of the steady-state entanglement could be achieved at a considerably lower driving power, which is also extremely robust with respect to the system parameters and environmental temperature. We then employ Gaussian quantum discord (QD) as a more genuine measure of the quantumness of the correlation.
[This work is published in JOSA B, Vol. 34,1503 (2017) and recognised as one of the top downloaded papers of 2018 in the journal.]

• Title of the talk: "Optical Tweezers"
Speaker: Prof. Bosanta R. Boruah
Date & Time: 9th October, 2018, 5:30 pm-5:45 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The technique/concept that led to first half of the Nobel Prize.

• Title of the talk: "Chirped Pulse Amplification"
Speaker: Prof. Amarendra K. Sarma
Date & Time: 9th October, 2018, 5:45 pm-6:00 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

The technique/concept that led to second half of the Nobel Prize.

• Title of the talk: "Impact of top quark in Diphoton production from gluon fusion at NLO"
Speaker: Dr. Manoj Mandal, Post doctoral fellow, IIT Guwahati
Date & Time: 27th September, Thursday, 5.15 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

We present a framework that allows to evaluate the next-to-leading order (NLO) corrections in QCD of the Di-photon production through gluon fusion, retaining full top quark mass effects, numerically. Our method starts from the generation of the necessary amplitudes followed by the reduction of the integrals using the Integration-By-Parts reduction and the numerical evaluation of the master integrals via combination of differential equation and sector decomposition. Specifically, we will show the results for the inclusive cross-section and the invariant mass distribution for the first time, thereby exhibiting the importance of the inclusion of the top mass effects.

• Title of the talk: "Universal Particle Localization Underlying Glass Formation."
Speaker: Dr. Tarak Patra, Post Doctoral Fellow,(ANL, USA)
Date & Time: September 13, Thursday, 5-6 pm
Venue: Seminar Room, Department of Physics
Abstract of the talk:

Despite more than half a century of research, the fundamental nature of the glass transition remains one of the major open questions in materials science and condensed matter physics. Computer simulations have provided key insights into this problem, but their ability to firmly establish the underlying nature of glass formation have been limited by the extreme computational difficulty of directly probing the deeply supercooled regime most relevant to this process. Here we describe a new protocol for simulation of the glass transition enabling facile access to in-equilibrium segmental relaxation times approaching and exceeding one microsecond - well into the deeply supercooled regime of most glass-forming liquids. Coupled with a well-validated strategy for extrapolation to experimental timescales, this approach provides vastly improved prediction of experimental glass transition temperatures. Here, we combine data acquired through this protocol for the deeply supercooled regime of polymeric, inorganic, organic, and metallic glass formers to identify microscopic phenomenological features shared across all classes of glass-forming liquid in the deeply supercooled regime. Further, correlations between glass formation and conductivity of polymeric materials are addressed.

• 27 Aug 2018, 5 pm: Weekly Seminar : Speaker Prof. Parongama Sen, Department of Physics, Calcutta University, Title of the talk: Nonequilibrium behaviour of classical spin models: some applications in social phenomena.
• 16 Aug 2018, 5 pm: Weekly Seminar : Speaker Dr. Saikat Chakraborty, IIT Kanpur, Title of the talk: Anisotropy evolution in $f(R)$ gravity.
• 14 Aug 2018, 5 pm: Weekly Seminar : Speaker Professor Achanta Venu Gopal, TIFR, Title of the talk: Broadband plasmonics in the optical and THz range.