Thermodynamics and small quantum systems

TL;DR

This paper explores how small quantum systems interacting strongly with their environment exhibit unique thermodynamic behaviors, including possible violations of classical inequalities and the potential for work extraction from the bath.

Contribution

It provides exactly solvable models demonstrating thermodynamic anomalies in small quantum systems coupled to baths, highlighting phenomena like inequality violations and work extraction.

Findings

Clausius inequality can be violated in quantum regimes

Negative energy dissipation rates are possible during non-adiabatic changes

Cyclic processes can extract work from quantum baths

Abstract

Small quantum systems non-weakly coupled to a bath become in the quantum regime surrounded by a cloud of photons or phonons, which modifies their thermodynamic behavior. Exactly solvable examples are the Brownian motion of a quantum particle in a harmonic confining potential and coupled to a harmonic quantum thermal bath, e.g. an ion in a Penning trap, and a spin immersed in a bosonic bath, as occurs in NMR physics. It appears that the Clausius inequality $\dbarrm Q\le T\d S$ can be violated. For non-adiabatic changes of system parameters the rate of energy dissipation can be negative, and, out of equilibrium, cyclic processes are possible which extract work from the bath. Experimental setups for testing some of the effects are discussed.