Driving Spin-Boson Models From Equilibrium Using Exact Quantum Dynamics

TL;DR

This paper applies an exact quantum dynamics method to spin-Boson models driven from equilibrium, revealing new transient and steady-state behaviors not captured by traditional approximations.

Contribution

It introduces a numerical implementation of the Extended Stochastic Liouville Equation for driven spin-Boson systems from equilibrium, expanding the modeling capabilities of open quantum systems.

Findings

Observed significant transient behaviors in the reduced density matrix.

Identified differences in asymptotic states compared to standard approximations.

Demonstrated the method's ability to handle arbitrary parameter regimes.

Abstract

We present an application of the Extended Stochastic Liouville Equation (ESLE) Phys. Rev. B 95, 125124, which gives an exact solution for the reduced density matrix of an open system surrounded by a harmonic heat bath. This method considers the extended system (the open system and the bath) being thermally equilibrated prior to the action of a time dependent perturbation, as opposed to the usual assumption that system and bath are initially partitioned. This is an exact technique capable of accounting for arbitrary parameter regimes of the model. Here we present our first numerical implementation of the method in the simplest case of a Caldeira-Leggett representation of the bath Hamiltonian, and apply it to a spin-Boson system driven from coupled equilibrium. We observe significant behaviours in both the transient dynamics and asymptotic states of the reduced density matrix not present in the usual approximation.