Areas of Research

The Department of Physics carries out research in diverse and emerging areas of science. Some of the major areas include condensed matter experiment, condensed matter theory, and high energy theory.

Experimental Condensed Matter Physics

Experimental condensed matter physics (CMP) is one of the key research areas of the department. Some of the topics of interest include amorphous and crystalline semiconductors, correlated electron systems exhibiting magnetism, superconductivity, metal-insulator transitions, colossal magnetoresistance, multi-functionality and phase transitions in oxide systems, novel 2D materials, thin films, etc. The group members are also working intensively in investigating multifunctional (ferromagnetic/ferroelectric / superconducting/optical / metal-insulator transition) oxide thin film heterostructures, spintronics device, electrostatic modification of materials, geometrically frustrated magnetic nanostructures and networks, electronic transport in mesoscopic devices and magnetism in reduced dimensions.

The state-of-the-art experimental facility is being developed to pursue research in the aforementioned areas. Pulsed laser thin film ablation system with LEED, single crystal growth furnaces using optical floating zone and Czochralski method, high resolution x-ray diffractometer, nanosecond laser system with optical parametric amplifier, Raman and Terahertz spectrometer with variable temperature and magnetic field, angle-resolvedphotoemission spectrometer, physical property measurement system and high sensitivity high speed SQUID magnetometer have already been procured.

Following are the different branches of experimental condensed matter physics of the department:

Electron Spectroscopy

The electron spectroscopy group is working on the study of electronic structure of condensed matter systems having novel properties such as metal insulator transitions, high-temperature superconductivity, unusual magnetism, non-Fermi liquid behaviour, charge and spin density wave state, etc., using high energy and angle resolved photoemission spectroscopy. The photoemission experiments using fixed photon energy are performed with various lab based x-ray and UV sources, and experiments involving variable photon energies are performed at synchrotron sources such as Elettra, Italy; UVSOR, Japan; AL Sand SRC, USA; etc. In addition to the experimental details, the band structure calculations and model calculations are also performed to get deeper insight and understanding of various ground state properties and solid-state phenomena.

Femtosecond VUV Molecular Science

The upcoming "Femtosecond VUV Molecular Science" laboratory will aim to generate to ultrashort laser pulses (< 25 fs) in the VUV and XUV spectral domain (below 200nm) and probe electronic and nuclear motion in molecules in real time using electron-ion coincidence imaging. The combination of VUV light and electron-ion imaging will facilitate the probing of the molecular states with complete kinematic information in the molecular frame of reference and provide insights on multi-electronic systems, correlation effects, nuclear coupling, dynamical symmetries, molecular chirality, etc.

Non-Linear Optics

The non-linear optics group works in the frontier areas of technological interest, namely, development and applications of optical spectroscopy and imaging techniques to explore non-linear properties and ultrafast photo-control of electronic processes in functional materials. In this area we are employing, cutting-edge terahertz technology, non-linear and time-resolved spectroscopy techniques, etc. These techniques are rapidly evolving and have proven applications and efficacy.

Besides the technological aspect, we are also investigating experimentally the physics behind the ultra-fast non-linear optical effects on both the microscopic and macroscopic levels and in the process learning how to control, tailor and enhance them.

Raman Spectroscopy of complex materials

Raman Spectroscopy group is interested in investigating some of the many-body effects in complex materials which include complex metal oxides and novel 2D materials. The group’s main focus is to study phonons and their interactions with various other quasi-particles, such as, electrons, magnons, orbitons, and others - and try to unravel their role in the novel properties of the complex materials. The group investigates such interactions using Raman spectroscopy in-situ/ex-situ with electron transport and magnetic measurements. Presently, the group is equipped with a micro-Raman spectrometer with a cryo-magnet which is capable of varying sample temperature from 5 to 300 K in combination with a magnetic field of up to 9 T. In addition, a liquid nitrogen-based cryostat is also available to explore these interactions at higher temperatures up to about 870 K.

Quantum Magnetometry

We develop nitrogen-vacancy (NV) spin-based diamond magnetometers capable of measuring minute magnetic fields with high sensitivity and spatial resolution. Our aim is to utilize diamond spins as scanning probes to spatially map tiny magnetic fields on the nanoscale. This would allow us to obtain a greater understanding of the magnetic phenomena which are otherwise not discerned by global magnetization measurements due to spatial averaging.
Our long term goals include setting up a cryogenic quantum magnetometer which would open the door for studying a variety of magnetic phenomena in condensed matter nanosystems, together with the possibility of making quantitative measurements. Some of the studies we imagine applying our magnetometer sensitivity and spatial resolution include probing magnetic phase transition in ferritin bioproteins, imaging edge magnetism in graphene, stray-field imaging of vortices in high-temperature superconductors and understanding emergent nanoscale magnetism in oxide heterostructures.

Strongly Correlated Electron Materials

Research is being carried out to study the properties of strongly correlated electronic materials including those exhibiting superconductivity, magnetism and other unconventional properties. Emphasis is on topological insulators and superconductors which have generated considerable scientific interest in recent years because of their various interesting properties. Three major avenues of research towards this direction are single crystal growth using floating zone, Czochralski, Bridgman, flux and vapor transport methods, measurements of magnetic, muon spectroscopy and neutron scattering (ISIS facility at Rutherford Appleton Laboratory U.K., III Grenoble France and PSI Switzerland) and thermodynamic and transport properties.

Terahertz Science of Complex Oxides

The primary research interest of the Terahertz group is in the application of Terahertz (THz) technology io condensed matter and material science to understand the ultrafast process and low energy dynamics. The integration of THz-spectroscopic and -imaging techniques with the materials of contemporary technological interests such as multiferroics, ferroelectrics and manganites presents opportunities to explore a new range of physical phenomena and appropriate industrial applications. THz-emission via ultra-fast 'femto-second laser pulse' modulated photo-current density, static and dynamic electric-fields and spin moments can directly probe the ultrafast functionality of the material specific parameter. Using time-resolved THz-emission and THz imaging, the ultrafast dynamics of photo-excited carriers, polarization and spin moments can be precisely determined. These studies facilitate understanding of the non-destructive control and the response time of electrical/magnetic memory to the femto-second laser stimulus. All such features are crucial to design futuristic ultrafast optical and hybrid opto electric/magnetic data storage devices.

Theoretical Condensed Matter Physics

On the theoretical side, research is being carried in a variety of fields. One emphasis is on the physics of strongly correlated electronic systems in low dimensional systems. In particular, the current focus of the group is to explore the possibility of realizing Majorana bound states at the ends of one-dimensional conductors formed by topological insulator edge states, semiconductor nanowires or carbon nanotubes in the proximity of a superconductor. The high interest in the field is due to the fact that Majorana particles which were proposed almost 80 years ago have so far proven to be elusive and for the first time there is a real optimism that they might be sighted in a solid state set-up. Infact, recent experiments do provide signatures of these elusive particles. The potential application of the Majorana edge states as elementary components of a topological quantum computer has generated lot of excitement. In this regard our group is working on the crucial questions regarding the stability of these Majorana states in the presence of impurity and electron-electron interactions. We are also developing schemes for the efficient manipulation and detection of the end states. In a parallel development the group is seeking an alternative to quantum dots in the form localized end states in density modulated quantum wires and rings.

A second broad emphasis is the exploration of concepts/ideas/techniques borrowed from the field of quantum information science in the context of familiar condensed matter systems. Quantum phase transitions, transport phenomena, quantum hall systems, topological phases, spin chains are but a small subset of concepts that are being studied from this perspective. The development and acquisition of many numerical and analytical techniques goes hand-in-hand with the pursuit of this philosophy.

A very important part of the activities in the theoretical condensed matter branch is to accurately calculate physical properties of real materials that can explain experimentally observed phenomena and predict new phenomena that may be experimentally verified. Using first principles techniques like density functional theory, quantum Monte Carlo simulations etc., a variety of physical properties like structural, magnetic, optical properties are accurately calculated for solids, nanomaterials, and heterostructures. This branch mainly relies on high performance computing for quantitatively estimating the physical properties for real materials using the underlying theories and works as a bridge between theory and experiment in condensed matter physics by making experimentally verifiable predictions.

Theoretical Soft Condensed Matter Physics

In the last few decades, soft-matter physics has evolved into an interdisciplinary research field comprising condensed matter physics, chemistry, biology, chemical engineering and material sciences. This field includes the study of nanometer to micrometer size objects such as polymers, biomolecules, colloids, membranes, self-propelled objects, glassy and amorphous materials, to name a few. Dynamical and mechanical properties of soft materials are of enormous importance not only from a fundamental physics point of view, but also due to their wide ranging applications across industries as diverse as pharmaceutical, paint industry, micro-fluidics of biological and synthetic materials etc.

The research in theoretical soft condensed matter group is focused on modeling and understanding of active polymers, colloids and vesicles in Newtonian/visco-elastic and active medium. Electrophoresis and diffusiophoresis mechanisms are employed to probe the role played by the activity and deformability of such objects. The findings of the research may be employed on ensembles of motors to perform tasks such as targeted delivery of cargo to a given location. When many motors are launched to perform a task the interactions among the motors must be taken into account. The research results indicate how such interactions influence the behavior and lead to active self-assembly, swarming, and distinctive correlations that depend on motor geometry. Furthermore, modelling of polymeric and colloidal suspensions include specific study of transport of polyelectrolytes in microfluidic devices, rheology of polymers and colloids, and transport of nano-composite materials. Techniques include in study of such systems are combination of analytical theory with coarse-grained hydrodynamic simulations (MPC), molecular dynamics simulations and, Brownian dynamics simulations.

Theoretical Atomic Physics

The theoretical atomic physics group specialises in quantum simulations and quantum dynamics of complex systems. We study ultra-cold setups with Bose-Einstein condensates, Rydberg atom assemblies or quantum opto-mechanics as well as hybrid systems of all these. The goal is to exploit these systems to simulate phenomena from other disciplines, such as condensed matter physics, (bio-)chemical physics or even quantum field theory in curved space-time. This is advantageous in situations where the ultra-cold atom experiments that we propose allow full control over system parameters, whereas theory or experiment in the original discipline may be intractable. Our work heavily relies on computer simulations to solve many-body quantum non-equilibrium dynamics.

Some of the faculty members in the Condensed Matter Physics group also work in interdisciplinary areas in collaboration with other departments of the institute.