Local moments in spin-orbit coupled systems

• Applicant: Dr. Toshihiro Sato, Ph.D.
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 435049553

The interplay of spin-orbit coupling and electronic correlations leads to a variety of phenomena of current research in solid state physics. Examples include fractionalization and associated emergent gauge theories in generalized Kitaev models relevant for iridates, as well as magnetic adatoms on the surface of strong topological insulators. In this grant proposal, we aim at using exact auxiliary-field quantum Monte Carlo simulations to investigate thermodynamic and dynamical properties of such systems. The general problem of electronic correlations in spin-orbit coupled systems suffers from a negative sign problem that renders it exponentially hard. Here, the key technical insight is that we can use symmetry arguments to reduce the severity of the negative sign problem. This will allow us to access the high-temperature thermodynamic and dynamical properties of the above-mentioned systems and, for instance, probe for signatures of exceptional points in the single-particle spectral function. As for the doped Hubbard model, we foresee that we will be able to reach experimentally relevant energy scales. Our approach is based on a fermion representation of the spin operator. Within our formulation, one can avoid the negative sign problem by attaching an even flavor index to the fermions. Another goal of the proposal is to investigate these models, and in particular to address the question if they capture aspects of the physics of the flavorless ones.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Fakher Fakhry Assaad