Abstract: We discuss the problem of surface-directed spinodal decomposition (SDSD), i.e., the interplay of wetting and phase separation in an AB mixture in contact with a surface which is wetted by one of the components (say, A). We present scaling arguments and numerical results to discuss the growth laws for the wetting layer which grows at the surface. We separately discuss cases where material is transported via (a) diffusion or (b) hydrodynamic velocity fields.

Abstract: Semiconductor nanostructures have drawn increasing attention since they provide a means to create artificial potentials for electrons and holes in semiconductors, at length scales comparable to exciton Bohr radius. Modern epitaxial techniques have made possible atomic scale features in the growth direction, and the advent of nanolithography has made feasible the control of lateral dimensions for the fabrication of quantum devices. Using the quantum confinement characteristics, new electronic and photonic devices with unique but tailored properties have become feasible with additional degrees of freedom in design. I shall discuss the progress of Si and two-dimensional (2D) transition metal dichalcogenides-based quantum photonic devices. The development of two-dimensional quantum hybrids for their applications in Si-compatible photonic devices using tunable light-matter interactions will also be discussed.

Abstract: Organic semiconductors are well known for their applications in OLED and solar cells. The advantage of using organic semiconductors are the low processing and fabrication cost due to solution processing and simple fabrication procedures. The low charge carrier mobility in these semiconductors is the bottleneck in organic semiconductor-based electronics. Devices based on organic semiconductors require band-level alignment for the injection of charge carriers, these charge carriers generally flow at the bottom of the Gaussian density of states (GDOS), which is the main cause of low charge carrier mobility. The problem can be addressed by filling the GDOS with charge carriers close to the center which makes the charge carrier mobility orders of magnitude higher. Organic field effect transistors have shown much higher mobility due to the accumulation of charge carriers in the GDOS which makes the center of GDOS accessible for transport.

Abstract: Correlated quantum systems define a frontier in many-body physics, where there is often no convincing theory even for equilibrium properties. Experiments however have moved on to probing the nonequilibrium properties of such systems, for example, the voltage bias-driven breakdown of a Mott insulator, or the pump-probe dynamics of charge density waves in a strong coupling electron-phonon system. I will present a couple of equation of motion approaches to such problems, one a Langevin scheme for thermal systems, another an explicitly energy-conserving dynamics for an isolated system.

Abstract: The main scientific motivations of the LHC project are to understand the physics of the electroweak symmetry breaking (EWSB) and to probe the nature of the fundamental interactions among elementary particles at TeV energy scale. Towards the first mandate, we have been extremely lucky. The Higgs boson was discovered at the LHC in 2012, within a short while of the start of the data-taking in 2009 by the ATLAS and the CMS experiments. Since then, extensive studies about the nature of this newly discovered particle bolstered the description of EWSB in the standard model. This talk will present the important aspects of this journey till now.

Abstract: Information may be understood as the ability to distinguish between possible alternatives reliably. This implies that different messages must be encoded by states of a physical system that can be reliably distinguished from one another. So information encoded in quantum states can only be perfectly retrieved when the quantum states are orthogonal, for no measurement can reliably distinguish between non-orthogonal states. In this talk, we will consider the situation where information is encoded in orthogonal states of a composite quantum system in a distributed setting, i.e. where parts of the system are held by observers separated from each other. We will present examples of orthogonal quantum states that cannot be reliably distinguished in this scenario, which implies the existence of locally hidden information and a new kind of quantum nonlocality that, in some cases may be viewed as dual to Bell-nonlocality.

Abstract: From quantum computation to communication, design of protocols and peripheral technology often rely strongly on the quantum interaction of light with matter. Hybrid quantum systems based on spin ensembles have shown exciting properties in the storage, transfer, and protection of information. In this talk, we show some theoretical results that demonstrate how a hybrid system can be engineered to allow for efficient transfer of quantum states of light to a mesoscopic spin ensemble and, in another instance, also allow for strong protection of the transferred quantum information.

Abstract: Neutrinos have been one of the most confounding particles of the Standard Model. They possess tiny masses established by the observation of neutrino flavour oscillations. To generate such tiny masses several mechanisms are proposed in literature including the famed seesaw mechanisms, radiative mechanisms, etc. While they are excellent in their own right, novel mechanisms are being proposed. These mechanisms aim to generate large hierarchies in relevant couplings assuming O(1) parameters in the fundamental parameters of the model/theory. The ideas are influenced from both physics of extra dimensions in particle physics to Anderson localization in condensed matter physics. The most striking of these are models based on fractal structures in theory space. After presenting these models, we discuss some possible signatures of them in various sectors like flavour factories, cosmology, and direct experiments like LHC.

Abstract: Nonlinear photonics experiments are not new as several ideas have been successfully commercialized. Our group has worked on multiple experiments in nonlinear photonics in the last 25 years; in this talk, I will present two specific examples from our work, related to the development of broadband lasers and UV- visible light generation. Even though a majority of lasers are quasi-monochromatic in nature, broadband lasers are also possible using nonlinear concepts; I will discuss one method. Coherent light sources emitting at different wavelengths in the ultraviolet (UV) range are not commonly available. I will discuss a method to generate UV light without involving second- or third-harmonic generation. This UV light is part of a correlated photon pair relevant to quantum communications.

Abstract: Over cosmic time, galaxies grow by merger, and/or by the accretion of matter via inflows. As galaxies evolve they also convert their gas into stars. On a cosmic scale, it is well established that the star formation peaked about 10 billion years ago and that the average star formation rate per unit volume has declined sharply since then. Hydrogen is dominant baryonic component of galaxies, and atomic hydrogen is also the primary fuel for star formation. Stars form as the gas cools to become molecular hydrogen, and then cools further and collapses into stars under self gravity. Understanding the evolution of the atomic hydrogen content of galaxies is hence key to understanding the evolution of the star formation rate with cosmic time, as well as the total baryonic content of star forming galaxies. Atomic hydrogen emits a spectral line at a wavelength of 21cm, (i.e. in the radio regime), which can be observed by radio telescopes, such as the Giant Metrewave Radio Telescope (GMRT), located near Pune. The recent upgrade to this telescope has allowed for significant progress to be made in our understanding of the evolution of gas in star forming galaxies. In this talk, I will discuss some of the results from ongoing atomic hydrogen surveys of star forming galaxies using the upgraded GMRT.