Currents and Green's functions of impurities out of equilibrium -- results from inchworm Quantum Monte Carlo

TL;DR

This paper extends the inchworm quantum Monte Carlo method to handle out-of-equilibrium impurity problems on the Keldysh contour, enabling accurate computation of Green's functions, spectral functions, and currents in time-dependent scenarios.

Contribution

The authors develop a generalized inchworm Monte Carlo algorithm for the full Keldysh contour, allowing systematic error assessment and application to out-of-equilibrium impurity dynamics.

Findings

Successfully computed Green's functions and currents after a voltage quench.

Demonstrated the method's ability to handle strongly correlated impurity dynamics.

Provided insights into impurity behavior out of equilibrium.

Abstract

We generalize the recently developed inchworm quantum Monte Carlo method to the full Keldysh contour with forward, backward, and equilibrium branches to describe the dynamics of strongly correlated impurity problems with time dependent parameters. We introduce a method to compute Green's functions, spectral functions, and currents for inchworm Monte Carlo and show how systematic error assessments in real time can be obtained. We then illustrate the capabilities of the algorithm with a study of the behavior of quantum impurities after an instantaneous voltage quench from a thermal equilibrium state.