Thermodynamics and Fluctuation Theorems for a Strongly Coupled Open Quantum System: An Exactly Solvable Case

TL;DR

This paper investigates the thermodynamics and fluctuation theorems in a strongly coupled open quantum system, providing an exactly solvable model that reveals novel behaviors like negative entropy and specific heat at low temperatures.

Contribution

It presents an exactly solvable model of an open quantum system with strong coupling, explicitly evaluates the Hamiltonian of mean force, and analyzes thermodynamic properties.

Findings

Validation of fluctuation theorem in the model

Explicit calculation of the Hamiltonian of mean force

Negative entropy and specific heat at low temperatures

Abstract

We illustrate recent results concerning the validity of the work fluctuation theorem in open quantum systems [M. Campisi, P. Talkner, and P. H\"{a}nggi, Phys. Rev. Lett. {\bf 102}, 210401 (2009)], by applying them to a solvable model of an open quantum system. The central role played by the thermodynamic partition function of the open quantum system, -- a two level fluctuator with a strong quantum nondemolition coupling to a harmonic oscillator --, is elucidated. The corresponding quantum Hamiltonian of mean force is evaluated explicitly. We study the thermodynamic entropy and the corresponding specific heat of this open system as a function of temperature and coupling strength and show that both may assume negative values at nonzero low temperatures.