The condensed matter group is mainly involved in studies on quantum matter. This includes modelling of materials, ab-initio computations and mesoscopic systems. Other interests include non-linear dynamics and statistical physics.
Correlated systems involve quantum matter where inter-particle interactions dictate physical properties. These include d and f electron materials, and artificially engineered cold atomic gases. Phenomena of interest include exotic magnetism, superconductivity, metal-insulator transitions, and unusual effects of disorder. The understanding of these materials is built on quantum many body theory and the use of advanced computational tools.
First principles studies of materials involve solving the many-electron interacting SchrC6ndinger equation. Hatree-Fock approximation and post-HF methods along with the density functional theory (DFT) form the canonical approach to such problems. But in the recent years other approaches, such as quantum Monte Carlo (QMC), have also emerged as alternatives for more accurate solutions to such problems. Methods have also been developed to include effects such as the strong electron-electron interactions on the d and f atomic orbitals of the transition metal atoms, and dispersion interactions, that traditional functionals within DFT cannot take care of. Our approach at HRI combines these methods depending on the complexity of the problem and the questions being asked.
In the recent years, our main focus has been on understanding properties of small atomic clusters, and identifying possible magnetic superatoms. We have also focused on graphene motivated 2D electronic materials such as hexagonal BN, or h-BN graphene hybrids. Occasionally, we have also studied bulk oxide materials such as PbPdO2, and KO2.
Low dimensional quantum systems are those where at least one spatial dimension is small enough so that the quantum nature of the wave-function becomes important. Examples include the layered semi-conductor systems which show the quantum hall effect, materials like graphene and its cousins, and topological insulators. They also include one-dimensional systems like quantum wires and zero-dimensional systems like quantum dots.
The research work at HRI strives to explore and understand the extra-ordinary and highly intriguing behaviour of these systems, which are very different from those of their bulk counterparts.
For many decades, the Landau paradigm of symmetry breaking has been the bedrock of classification of how atoms in a material organise themselves. But in the last decade or so, it has been recognised that there are phases of matter which are topologically ordered and go beyond the Landau classification. These phases have interesting properties like ground state degeneracies, abelian and non-abelian fractional statistics and edge states, and they have potential application in quantum computation.
Since many of these materials require spin-orbit coupling, one focus of research in HRI is on understanding naturally occuring spin-orbit as well as engineered pseudo-spin orbit coupling in solid state systems as well as in optical lattices.
Nonlinear dynamics can be described as a set of techniques that one uses to address problems where the mathematical description requires the study of nonlinear differential equations or maps. The conventional meaning somehow seems to restrict it to systems described by maps and ordinary differential equations. Such a restriction would , however, rule out the notoriously problematic fully developed turbulence from the ambit of nonlinear dynamics.
In HRI, we interpret nonlinear dynamics as the study of any system where the time development ( continuous or discrete) is dominated by nonlinearity. Thus conservative and non-conservative dynamical systems, hydrodynamic instabilities, turbulence, growth models, pattern formation, dynamic critical phenomena near or far from equilibrium, dynamics of trapped condensates etc all come under the same umbrella.
My current interests are in studying scales and scaling in convective turbulence, looking at efficient use of renormalization group techniques in describing dynamical systems , understanding the classical and quantum dynamics of an extensible pendulum and describing wave packet dynamics in Gross Pitaevski equations.
The work at HRI is mainly on Mott systems, inhomogeneous order in superconductors, magnetism, and other cooperative states in correlated matter. We also work on developing alternate approaches, both analytical and numerical, to the many body problem.
My interest lies in exploring phases and phase transitions in quantum matter. We try to understand the interplay between electron correlations and electron-lattice coupling, effect of disorder on superconductivity, and novel phases in cold atom condensates in optical lattices.
Currently we are studying topological excitations arising in spin-spce Entangled liquids using recently developed Quantum Non-Abelian Hydrodynamics description of generic "SO Hamiltonians" which goes beyond the adiabatic approximations. In this approach both fermionic and bosonic non-abelian topological excitations occurs which are closely related to non-unitarity of scattering matrix in spin space.
The current focus is on quantum wires and edge states, topological states of matter including Weyl semi-metals, quantum Hall states and interferometry, Majorana fermions and non-abelian states. Newer analogs of graphene like silicene and Kitaev-like models leading to spin liquids are also being studied.
Our current focus is on two different systems. We are studying clusters deposited on substrates. Understanding cluster properties on the substrate supports is important for many applications including catalysis, magnetic storage, chemical sensor etc. We are also studying the newly synthesized 2D material phosphorene. Phosphorene overcomes many of the drawbacks that make graphene unsuitable for application in the FET channel. We are trying to understand properties of phosphorene nano-ribbons, and metal-phosphorene interfaces.
Secretary, Condensed Matter Group
Harish-Chandra Research InstituteChhatnag Road, JhunsiAllahabad, India- 211019 +91-532-227-4348