Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic

报告摘要：

Quantum dynamics in many-body interacting systems reflects the non-commutativity of the operators of kinetic energy and particle interaction of their Hamiltonians. It is present only in theories beyond the Hartree-Fock mean-field approximation. The paradigm theory of superconductivity of Bardeen, Cooper, and Schrieffer (BCS) does not contain any quantum dynamics. One must go beyond this approximation to include quantum dynamics in superconducting materials, particularly in strongly-correlated electron systems. Dynamical extensions of the BCS theory of superconductivity suffer, however, from the discrepancy between the critical point calculated from the disordered high-temperature and ordered low-temperature phase. We present a way to correct this deficiency in a generic Hubbard model with attractive interaction.

We first analyze self-consistent dynamical approximations to show that the generic difference between the dynamical and conserving two-particle vertices is responsible for their inability to consistently match the ordered and disordered phases at the critical point. We propose a solution to this problem and show how to modify the contributions from the anomalous Green functions in the ordered phase to guarantee the order parameter's emergence at the critical point of the superconducting susceptibility from the high-temperature phase. We exemplify this construction on the Landau expansion in second-order dynamical mean-field theory.

报告人简介：

Prof. Václav Janiš, a distinguished Condensed Matter theorist and senior researcher at the Institute of Physics of the Czech Academy of Sciences, has significantly contributed to the field of non-relativistic quantum many-body theory. His extensive experience focusing on non-perturbative methods, many-body Green functions, and collective and critical phenomena of strongly correlated electrons has pushed the boundaries of knowledge. His research interests include quantum dynamics in Fermi systems with broken symmetry and long-range order, superconductivity, itinerant magnetism, charge diffusion, spin glasses, and quantum critical behavior. His research results are at the forefront of theoretical investigations in the physics of correlated electrons. https://orcid.org/0000-0001-5959-6935

联 系 人：朱北沂 8264-9927