Bath generated work extraction in two-level systems

TL;DR

This paper demonstrates that in a spin-boson model, external pulses can extract work from a thermal bath in a way that violates traditional thermodynamic laws, highlighting quantum effects in work extraction.

Contribution

It introduces a solvable model showing work extraction from a thermal bath via pulses, violating classical thermodynamic principles in a quantum two-level system.

Findings

Work can be extracted on the T_2 timescale.

Extraction involves heat from the bath with constant spin entropy.

Violates Clausius inequality and Thomson's second law in this context.

Abstract

The spin-boson model, often used in NMR and ESR physics, quantum optics and spintronics, is considered in a solvable limit to model a spin one-half particle interacting with a bosonic thermal bath. By applying external pulses to a non-equilibrium initial state of the spin, work can be extracted from the thermalized bath. It occurs on the timescale T_2 inherent to transversal (`quantum') fluctuations. The work (partly) arises from heat given off by the surrounding bath, while the spin entropy remains constant during a pulse. This presents a violation of the Clausius inequality and the Thomson formulation of the second law (cycles cost work) for the two-level system.