Speaker
Description
The exact dynamics of many-particle quantum systems coupled to an environment is governed by the Kadanoff-Baym equations. While these equations can, in principle, be solved exactly for small systems, the numerical cost grows rapidly and becomes prohibitive for longer times or larger systems. Beyond many-body correlations, the primary computational challenge arises from memory effects, which cause the numerical complexity to scale cubically with physical time. In certain cases, this scaling can be reduced to linear by reconstructing the lesser and greater Green’s function components from the electron density, however, at the expense of losing spectral information. It is demonstrated here that the Kadanoff-Baym equations for open systems can be solved numerically exactly with optimal quadratic time scaling, without introducing any approximations [Phys. Rev. B 113, L161111 (2026)].
As the first illustration, I will consider a correlated single-level quantum dot (QD) in the Coulomb blockade regime treated within the adiabatic TDDFT with the BALDA XC potential, and present two-time Green's functions and transient spectral functions for different bias voltages and temperatures. Then I will demonstrate that KBE are also compatible with nonadiabatic TDDFT treatment of the QD. Finally, I will discuss possible extensions of the idea towards correlated systems.