Thermodynamic anomaly of the free damped quantum particle: the bath perspective

TL;DR

This paper investigates the negative specific heat phenomenon in a damped quantum particle by examining the environment's response, providing a physical interpretation based on the bath's total mass and the system's mass.

Contribution

It offers a novel perspective by focusing on the environment's changes rather than the system alone, explaining the mechanism behind negative specific heat in open quantum systems.

Findings

Negative specific heat can occur at low temperatures in a damped quantum particle.

The mechanism involves the interplay between bath oscillator mass and system mass.

A formal condition for negative specific heat is derived with a physical interpretation.

Abstract

A possible definition of the specific heat of open quantum systems is based on the reduced partition function of the system. For a free damped quantum particle, it has been found that under certain conditions, this specific heat can become negative at low temperatures. In contrast to the conventional approaches focusing on the system degree of freedom, here we concentrate on the changes induced in the environment when the system is coupled to it. Our analysis is carried out for an Ohmic environment consisting of harmonic oscillators and allows to identify the mechanism by which the specific heat becomes negative. Furthermore, the formal condition for the occurrence of a negative specific heat is given a physical interpretation in terms of the total mass of bath oscillators and the system mass.