Quantum dissipative dynamics of a bistable system in the sub-Ohmic to super-Ohmic regime

TL;DR

This paper explores how a multilevel bistable quantum system's dynamics are influenced by different types of heat bath spectral densities, revealing complex dependencies in relaxation and tunneling behaviors.

Contribution

It introduces a non-perturbative analysis of quantum dissipative dynamics across a range of spectral densities using the Feynman-Vernon path integral method.

Findings

Short-time behavior depends on bath spectral properties.

Relaxation time scales vary nontrivially with spectral density.

Crossover regime shows damped oscillations and incoherent tunneling.

Abstract

We investigate the quantum dynamics of a multilevel bistable system coupled to a bosonic heat bath beyond the perturbative regime. We consider different spectral densities of the bath, in the transition from sub-Ohmic to super-Ohmic dissipation, and different cutoff frequencies. The study is carried out by using the real-time path integral approach of the Feynman-Vernon influence functional. We find that, in the crossover dynamical regime characterized by damped \emph{intrawell} oscillations and incoherent tunneling, the short time behavior and the time scales of the relaxation starting from a nonequilibrium initial condition depend nontrivially on the spectral properties of the heat bath.