Tsung-Han Lee, Rutgers University

(Virtual seminar)

Two-particle response functions are important physical quantities encoding the fingerprint of the collective excitations in physical systems. The advance of experimental techniques made it possible to measure the two-particle response functions in materials, e.g., the charge and spin susceptibilities from resonant inelastic X-ray scattering. However, it is still challenging to compute theoretically reliable two-particle quantities for strongly correlated materials. In this talk, I will present an efficient quantum embedding method for computing the two-particle response functions and quasiparticle interaction vertex for correlated systems, based on the Gaussian fluctuation around the rotationally-invariant slave-boson (RISB) saddle-point [1]. I will also present the application of our approach for explaining the pairing mechanisms of the s-wave orbital-antisymmetric spin-triplet superconductivity in Hund's coupling-induced bad metals and the collective charge and spin excitations in multiorbital systems. Our method can be combined with density functional theory and paves a way to investigate the collective excitations and the superconductivity in correlated materials.

[1] Tsung-Han Lee, Nicola Lanata, Minjae Kim, Gabriel Kotliar, arXiv:2104.02762 (2021) (Accepted by PRX, in Production)