Upcoming Colloquium

  • Title of the talk: "Quantum walks in one dimension: randomness, memory and a few surprises"
    Speaker: Prof. Parongama Sen, Department of Physics, University of Calcutta, India
    Date & Time: 19 January 2021, 05:00 PM
    Platform: MS Team
    Facebook live streaming: #Physics_IITG
    YouTube live streaming: #YouTube
    Abstract of the talk:

    We will begin by introducing the quantum walk, its most significant behaviour and some applications. Then we will move on to discuss some recent results where the quantum walker is allowed to take steps of variable lengths at each discrete time step randomly. Finally we discuss how a persistent quantum random walker behaves using two different schemes. The studies lead to some surprising results, which is quite characteristic of a quantum walk!

Past Colloquium

  • Title of the talk: "Universal Theories and Multiscale Description of Nature"
    Speaker: Prof. Mahendra K. Verma, Department of Physics, IIT Kanpur, India
    Date & Time: 12 January 2021, 05:00 PM
    Platform: MS Team
    Facebook live streaming: #Physics_IITG
    YouTube live streaming: #YouTube
    Abstract of the talk:

    Physicists have attempted to construct minimalistic laws to describe varied phenomena of nature. In history of science, there have been successes in this direction-—Newton's universal law of gravitation, Maxwell’s unification of EM laws, Unification of forces, etc. Symmetries play an important role in such description. But, can we explain all the natural phenomena starting from fundamental laws? In this talk, I will present different perspective.

    It turns out that many interesting phenomena such as time asymmetry, origin of dissipation (including quantum), symmetry breaking, etc. can be demonstrated quite easily under the framework of multiscale description. One important example of multiscale system is turbulence where the energy fed at large scale cascades to small scales, where it is dissipated by microscopic interactions.

  • Title of the talk: "Dynamics of Rydberg atoms: Role of quantum scars"
    Speaker: Prof. Krishnendu Sengupta, Department of Physics, Indian Association for the Cultivation of Science, Kolkata
    Date & Time: 25 November 2020, 04:00 PM
    Platform: Google Meet link
    Facebook live streaming: #Physics_IITG
    YouTube live streaming: #YouTube
    Abstract of the talk:

    In this talk, we are going to provide a pedagogical introduction to the physics of a chain of ultracold Rydberg atoms. This will be followed by a discussion of their dynamical properties and the role played by a special class of states, quantum scars, in shaping their details. Finally, we shall discuss such systems in the presence of a periodic drive and show that the drive frequency can be used to tune their ergodicity property. In addition, the driven systems show several phenomena such as dynamical freezing and sub-thermal steady states. We shall discuss this and chart out experiments which can test these theoretical predictions.

  • Title of the talk: "The Neutron Decay Anomaly: how it may be a window to new Physics"
    Speaker: Prof. Benjamin Grinstein, Department of Physics, University of California, San Diego, USA
    Date & Time: 18 November 2020, 10:00 AM
    Youtube Channel: Link to Talk
    Facebook live streaming: #Physics_IITG
    Abstract of the talk:

    In this talk I will first review a long-standing discrepancy between the neutron lifetime as measured in beam and in bottle experiments. If this discrepancy is not due to a systematic error, it may be due to novel mechanisms for neutron transmutation into new, as yet unknown elementary particles. These particles would be electrically neutral, or so-called “dark”. We will explain several scenarios for the possibility of neutron transmutation into dark particles. For example, in one interesting scenario the products of the neutron transmutation include a monochromatic photon with energy in the range 0.782 MeV–1.664 MeV and this is predicted to occur in 1% of all neutron decays. We will describe recent theoretical developments as well as ongoing and planned experiments looking directly to establish or rule out the “dark decay” hypothesis.

  • Title of the talk: "Using Descriptors to Design Novel Nanomaterials"
    Speaker: Prof. Shobhana Narasimhan, Theoretical Sciences Unit and School of Advanced Materials, JNCASR Bangalore, Bengaluru
    Date & Time: 11 November 2020, 04:00 PM
    Youtube Channel: Link to Talk
    Facebook live streaming: #Physics_IITG
    Abstract of the talk:

    Through much of history, novel materials have been discovered either by accident or through a process of trial and error. Worldwide, efforts are now underway to replace this by a program of rational materials design. In this endeavor, considerable time and effort can be saved by developing “descriptors” that, though possibly approximate, are quick to compute. Using descriptors, one can rapidly identify candidate materials that are likely to possess a target property, saving time when compared to experiments or first principles calculations. I will briefly review the field, and present work in my group on formulating descriptors for the structure of self assembled monolayers of organic molecules on surfaces and descriptors for the morphology and activity of Nanocatalysts.

  • Title of the talk: "Organic-inorganic hybrid pervoskites: A wonder material"
    Speaker: Prof. Dipankar Das Sarma, Solid State and Structural Chemistry Unit, IISc Bangalore, Bengaluru
    Date & Time: 04 November 2020, 04:00 PM
    Youtube Channel: YouTube link to Talk
    Facebook live streaming: #Physics_IITG
    Abstract of the talk:

    The last decade has seen the most spectacular rise of a class of materials, known as the hybrid halide perovskites. Their photovoltaic and light emissive properties have reached superlative levels of performance within this exceptionally short span of time and taken the world by surprise.

    Along with the intense effort to further improve the efficiency, stability and other technological aspects, there is a considerable effort in understanding the origin of such exceptional attributes. Curiously enough, there does not appear to be any universally accepted understanding of even the most basic properties of these materials. For example, an intensely debated issue concerns the ability of permanent dipoles on organic moieties to give rise to polar fields, either in the normal state (as in any ferroelectric material) or in the photo-excited state, contributing to its spectacular photovoltaic properties. Even estimates of the excitonic binding energy in these materials have proven to be controversial with various estimates differing by more than an order of magnitude. In a similar vein, while the stability issue has been addressed to a large extent by the substitutional chemistry at the A-site of the perovskite, its implications for various fundamental properties have not yet been clearly elucidated.

    I shall provide a detailed account of this field to underline the reasons for unprecedented excitement with these materials before introducing some of the open issues. I shall follow this up by discussing some of our efforts to resolve these puzzles.

    This work is a result of collaborations with B Bhattacharyya, M Bokdam, C De, C Franchini, S Ghara, TN Guru Row, A Hossain, BP Kore, G Kresse, A Kumar, J Lahnsteiner, P Mahale, A Mohanty, S Mukherjee, R. Mukhopadhyay, S Pal, A Pandey, MS Pavan, S Picozzi, T Sander, Sharada G, V. K. Sharma, A Stroppa, A Sundaresan, and D Swain.

    Relevant references:
    1. M Bokdam et al., Sci. Rep. 6, 28618 (2016).
    2. J Lahnsteiner et al., Phys. Rev. B 94, 214114 (2016).
    3. Sharada G et al., J. Phys. Chem. Lett. 7, 2412 (2016).
    4. Sharada G et al., J. Phys. Chem. Lett. 8, 4113 (2017).
    5. Sharada G et al., J. Phys. Chem. C 122, 13758 (2018).
    6. A Mohanty et al., ACS Energy Lett. 4, 2045 (2019).
    7. V. K. Sharma et al., J. Phys. Chem. Lett. 2020 (DOI: 10.1021/acs.jpclett.0c02688)
    8. Unpublished results from the group.

  • Title of the talk: "Three questions, one answer: Neutrinos as the key to the universe as we know it"
    Speaker: Prof. Yuval Grossman, Indian Institute of Science, Department of Physics, Cornell University, New York, USA
    Date & Time: 21 October 2020, 06:30 PM
    Youtube Channel: Link to Talk
    Facebook live streaming: #Physics_IITG
    Abstract of the talk:

    There are three open questions in physics which seem unrelated: Why is there only matter around us? How neutrinos acquire their tiny masses? Why all particles in Nature have integer electric charges? It turns out that these open questions are related. In this talk, I will explain these open questions, the connection between them, and describe the on-going theoretical and experimental efforts in understanding them.

  • Title of the talk: "Engineering the flow of charge, light and heat with atomic layers"
    Speaker: Prof. Arindam Ghosh, Indian Institute of Science, Bangalore, India
    Date & Time: 14 October 2020, 04:00 PM
    Youtube Channel: Link to Talk
    Facebook live streaming: #Physics_IITG
    Abstract of the talk:

    Van der Waals heterostructures represent a new paradigm of material design, where two atomic or molecular planes of different chemical origin are brought together within the sub-nanometer van der Waals distance. When two atomic layers are placed so close their electronic states may hybridize, and the physical properties are modified by the rules of momentum conservation and structural commensurability. In this talk I shall present several new physical phenomena, in multiple domains ranging from electronic, opto-electronic to thermoelectric properties, that emerge as a result of van der Waals heterostructuring of two-dimensional (2D) materials. Apart from achieving high carrier mobility and ultra-low noise in electrical transport, encapsulating graphene by boron nitride leads to manifestation of edge transport and trigonal warping at low energies. Optoelectronic properties are strongly enhanced on graphene and transition metal dichalcogenide heterostructures, that can be extended to single photon detection. I shall also show new phenomena in thermoelectric transport in twisted bilayer graphene, where the Seebeck coefficient is strongly determined by the angular misorientation between the graphene layers in the van der Waals stack.

  • Title of the talk: "Skyrmions -- classical crystals and quantum liquids"
    Speaker: Prof. Arun Paramekanti, University of Toronto, Canada
    Date & Time: 30 September 2020, 06:30 PM
    Youtube Channel: Link to Talk
    Facebook live streaming: #Physics_IITG
    Abstract of the talk:

    Skyrmions are topological textures which were first proposed in field theory as a model to understand nucleons and their stability. In recent years, skyrmions have been discovered as spin textures in magnetic solids, with potential applications in the form of `topological memories'. In this colloquium I will discuss the physics of single skyrmions, their crystalline orders, and how quantum melting of skyrmions may induce unusual quantum magnetic liquids.

  • Title of the talk: "Quantum Synchronization: A shared quantum rhythm"
    Speaker: Prof. Saikat Ghosh, Indian Institute of Technology, Kanpur, India
    Date & Time: 23 September 2020, 04:00 PM
    Youtube Channel: Link to Talk
    Facebook live streaming: #Physics_IITG
    Abstract of the talk:

    In this talk, we will discuss two seemingly disconnected but well studied topics and show how they can be connected towards observing a new physical effect. The first topic is a physical effect called synchronization, widely observable in nature everywhere and all the time. The second topic is related to the quantum world, where things behave very differently than what we see in our surrounding life. Recently, such quantum world behaviour is also being actively used towards building quantum computers and quantum communication devices. This has led to a new field of quantum technologies.

    After introducing these two topics, I will discuss what it means to observe such synchronization in the quantum world and what are the consequences of such quantum synchronization of spins and atoms in today's cutting-edge quantum technologies. I will end the seminar with a discussion of experimental results from our laboratory at IIT-Kanpur, that led to the very first observation of quantum synchronization.

    References:
    1. Arif Warsi Laskar, Niharika Singh, Arunabh Mukherjee and Saikat Ghosh, New J. Phys. 18, 053022 (2016).
    2. Arif Warsi Laskar, Niharika Singh, Pratik Adhikary, Arunabh Mukherjee and Saikat Ghosh Optica, 5, 1462 (2018).
    3. Arif Warsi Laskar, Pratik Adhikary, Suprodip Mondal, Parag Katiyar, Sai Vinjanampathy and Saikat Ghosh, Phys. Rev. Lett. 125, 013601 (2020).

  • Title of the talk: "Quantum Matter and P.W. Anderson (1923-2020)"
    Speaker: Prof. Ganapathy Baskaran, IMSc., Chennai, IIT Madras, Perimeter Institute of Theoretical Physics, Waterloo, Canada
    Date & Time: 16 September 2020, 04:00 PM
    Youtube Channel: Link to Talk
    Facebook live streaming: #Physics_IITG
    Abstract of the talk:

    Quantum matter refers to a piece of rusted iron, a grain of sand or a drop of water etc. By thinking deeply about these earthly materials and combining valuable clues from experimental results, P.W. Anderson, a theoretical physicist and a quantum mechanic par excellence helped discover some secrets of nature: origin of mass of elementary particles (electron etc.), glitches in pulsar periods, magnetism, superconductivity, science of complexity etc. His works exemplified hierarchical nature of science rather deeply. I will weave a story and share some personal anecdotal experiences with this remarkable and humane Nobel Laureate.

  • Title of the talk: "Dynamical Systems, Turbulence and Active Matter"
    Speaker: Prof. Jayanta K. Bhattacharjee, IACS, Kolkata
    Date & Time: 02 September 2020, 04:00 PM
    Youtube Channel: Link to Talk
    Facebook live streaming: #Physics_IITG
    Abstract of the talk:

    Turbulence in fluids has long been a difficult issue for theoreticians. The problem has been one of asking the right question to which an answer can be found in universal terms- a cherished goal of theorists. In 1941, Kolmogorov asked one such question and found an answer which is still not comfortably understood. A different set of questions ,which had experimental support, dealt with the problem of how a flow gradually becomes turbulent. This is where the dynamical system approach, initiated more than fifty years ago, was supposed to be an effective tool but did not quite fulfil one’s expectations. Recent applications to active matter suspensions raise some new hopes.

  • Title of the talk: "Satyendra Nath Bose : a Forgotten Hero"
    Speaker: Prof. Sreerup Raychaudhuri, TIFR, Mumbai
    Date & Time: 27 August 2020, 04:00 PM
    Youtube Channel: Link to Talk
    Facebook live streaming: #Physics_IITG
    Abstract of the talk:

    The life, times and scientific work of Satyendra Nath Bose (1894 - 1974) will be described in this talk. We shall start with an introduction to the quantum theory of blackbody radiation, where Bose made his epoch-making contribution. We will then take a look at the early life of Bose and the fertile intellectual milieu which created this man of genius. The story of his famous discovery of Bose statistics will then be taken up. The last part of the talk will be a panorama of Bose’s later life as a national celebrity, but a largely-forgotten figure on the international scene. We shall conclude with some critical comments on the story of this great scientist and his legacy.

  • Title of the talk: "Hunt for the Dark Matter of the Universe"
    Speaker: Dr. Subhaditya Bhattacharya of DEPARTMENT OF PHYSICS, IIT GUWAHATI
    Date & Time: 19 August 2020, 04:00 PM
    Youtube Channel: Link to Talk
    Facebook live streaming: #Physics_IITG
    Abstract of the talk:

    Dark Matter is the most illusive form of matter to constitute almost 23 percent energy budget of the universe. Compare it with roughly 4% of visible matter that we know of. Different astrophysical evidences have indicated the existence of Dark Matter although we have very little idea of what exactly it is. The talk will illustrate some possibilities what Dark Matter can be, as fundamental particle and what are the search strategies of Dark Matter in different experiments currently underway.

  • Title of the talk: "Understanding the biology of avian paramyxovirus for the development of recombinant vaccine"
    Speaker: Dr. Sachin Kumar of DEPARTMENT OF BIOSCIENCE AND BIOENGINEERING, IIT GUWAHATI
    Date & Time: 12 August 2020, 04:00 PM
    Youtube Channel Link to Talk
    Facebook live streaming: #Physics_IITG
    Abstract of the talk:

    Animal viruses are tiny packages of protein and nucleic acid. Avian paramyxovirus type 1 (APMV-1) causes Newcastle disease (ND) in chicken. ND is one of the highly pathogenic viral diseases of avian species. ND is economically significant because of mortality and morbidity associated with it. APMV-1 belongs to the family Paramyxoviridae and the genus Avulavirus. Recent advances in recombinant DNA techniques have brought forward to an era of new vaccine technology in modern medicine. One attractive strategy is the application of reverse genetics to make recombinant APMV (rAPMV). rAPMV can deliver protective antigens of pathogens in host and evoke a protective immune response. The rAPMV vaccine offers a pertinent choice for the construction of live attenuated vaccine due to its minimum recombination frequency, modular nature of transcription and lack of DNA phase during its replication. APMV is also explored widely in the field of cancer biology due to its property of replicating selectively in tumor cells. In the recent years, the reverse genetics technology allowed to generate rAPMV having high tumor suppressor property. By understanding APMV molecular biology, it is feasible to develop gene-modified recombinant vaccines possessing better safety and immunity for both animals and humans.