Theory of Ground State and Spectroscopic Properties of Strongly Correlated Electrons Systems | Department of Physics

Theory of Ground State and Spectroscopic Properties of Strongly Correlated Electrons Systems

The research in our group can be broadly classified as Theoretical Condensed Matter Physics. More specifically, our research focuses on the field of strongly correlated electron systems, where electron-electron interactions cannot be treated as a perturbation to its motion in the crystal potential, resulting in the breakdown of conventional band-structure description for such systems, at least in the rigourous sense.

On one hand, this field helps us to better understand emergent phenomena that can arise out of strong, non-perturbative interactions between electrons in narrow-band solids, like compounds of transition metals, rare-earths and actinides. The hallmark of this is seen in exotic phenomena like colossal magnetoresistance in the Manganites, high-temperature superconductivity in the Cuprates, spin-charge separation and charge fractionalization in low-dimensional correlated systems, and the Kondo effect, to name a few. In such phenomena one simply cannot think of each electron independently, but must take into account the collective behaviour of a macroscopically large number (~ Avogadro's Number) of electrons, all acting in unison. On the other hand, a basic understanding of the physics of these materials helps in designing “smart materials” with advanced and energy-efficient functionalities.

Since treating the full correlation problem for an infinite solid is an unsolvable problem, the challenge for theory is to continuously develop newer and more efficient analytical approximations and numerical techniques to better understand the properties of these “quantum materials”, as constantly emerging from experiments. We have been working in this field for more than a decade, trying to model the ground state (low-energy) as well as the spectroscopic (high-energy) properties of correlated electron systems, in collaboration with leading experts in the field, both in India and abroad. We are interested both in model problems as well as in complex real materials. At present our research interests and efforts are directed towards the following broad areas :

  • Electronic and Magnetic Properties of Strongly Correlated Electron Systems : Including mixed-valent systems, systems with strong spin-orbit coupling (e.g., 4d and 5d transition metal oxides), systems exhibiting exotic spin-orbital and hidden order.
  • Modeling of X-ray Spectroscopies : e.g. XAS, AES, XPS, NIXS, RIXS etc. and optical conductivity (normal and high-energy) in strongly correlated systems.
  • Spin/orbital Magnetism and Magneto-crystalline Anisotropy in Nano-structured Materials : e.g., surfaces/thin-films/multilayers/nano-particles etc.
  • Development of New Computational Tools for Correlated Electron Systems