Macroscopic Quantum Violation of Fluctuation-Dissipation Theorem in Equilibrium

TL;DR

This paper demonstrates that in certain macroscopic quantum systems, the fluctuation-dissipation theorem can be significantly violated even near equilibrium, revealing a genuine quantum phenomenon with implications for fundamental physics and practical noise estimation.

Contribution

The study shows macroscopic quantum violations of the FDT in equilibrium, extending the understanding of quantum effects on linear response and fluctuation relations.

Findings

Large-scale FDT violation observed at low temperatures and strong magnetic fields

Violation magnitude can surpass the Hall conductivity itself

Provides a necessary condition for such violations in general systems

Abstract

We examine the Hall conductivity of macroscopic two-dimensional quantum system, and show that the observed quantities can sometimes violate the fluctuation dissipation theorem (FDT), even in the linear response (LR) regime infinitesimally close to equilibrium. The violation can be an order of magnitude larger than the Hall conductivity itself at low temperature and in strong magnetic field, which are accessible in experiments. We further extend the results to general systems and give a necessary condition for such large-scale violation to happen. This violation is a genuine quantum phenomenon that appears on a macroscopic scale. Our results are not only bound to the development of the fundamental issues of nonequilibrium physics, but the idea is also meaningful for practical applications, since the FDT is widely used for the estimation of noises from the LRs.