Dr. Tanmoy Das

Department of Physics, Indian Institute of Science, Bangalore

E-mail: tnmydas[at]gmail.com

 

Brief Bio-sketch:

Das is a condensed matter theoretical physicists working in the areas of strongly correlated materials, superconductivity, topological insulators, non-Hermitian quantum systems. He as written about 100 journal papers on these areas. Some of the key papers include Topological Band Theory published in Review Modern Physics in 2016. He has introduced new ideas such as spin-orbit density wave, valence-fluctuation driven attractive potential as a new mechanism of superconductivity, non-Hermitian superconductivity, momentum dependent density fluctuation theory. He has received many awards including Infosys Young Investigator Award in 2017.

SYMMETRY-INVARIANT QUANTUM PHASES, SYMMETRY-BROKEN TOPOLOGICAL PHASES, AND OTHER SURPRISES OF QUANTUM MATTERS

When we think of a quantum phase transition, usually we think of pairings between electrons or electron-hole pairs, which essentially break one or more symmetries. On the other hand, when we consider topological phases, we look into symmetry invariance and fractionalization of fermions. In this talk, I shall discuss how a combination of DFT and low energy modelling enables us pushing the boundary beyond the conventional way of studying topological and quantum phases of matter. I shall point out, through examples, how certain topological phases can sustain to breaking the underlying symmetry and also the other way around. In fact, both topological excitations such as fractional anions, axions and quantum modes such as Higgs, paramagnon evolve hand-in-hand under such circumstances. I shall show a derivation of Chern-Simons-Ginsburg-Landau function from DFT inputs for TlCuCl₃. Similarly, I shall discuss our prediction of a bulk material in which an underlying topological phase leads to new quantum order, called antiferroelectricity without breaking inversion symmetry. I shall conclude with general perspectives on how the DFT methods can be utilized and exploited to realistically identify such topological and quantum instabilities, and how one can procced towards the future direction of computing various matrix-elements and form-factor for their realistic experimental visualization within DFT.

References :

1. A. Bansil, H. Lin, T. Das, Colloquium: Topological Band Theory, Review of Modern Physics 88, 021004 (2016).
2. G. K. Gupta, K. Dolui, A. Kumar, D. D. Sarma, T. Das, Higgs-Axion conversion and anomalous magnetic phase diagram in TlCuCl3, arXiv:1805.00166.