Fluctuation-dissipation relation in a non-equilibrium quantum fluid
arXiv:2305.06406 · doi:10.1103/PhysRevLett.131.244001
Abstract
There is no simple fluctuation-dissipation theorem (FDT) for nonequilibrium systems. We show that for a fluid in a nonequilibrium steady state (NESS) characterized by a constant temperature gradient there is a generalized FDT that relates commutator correlation functions to the bilinear response of products of observables. This allows for experimental probes of the long-range correlations in such a system, quantum or classical, via response experiments. We also show that the correlations are not tied to thermal fluctuations but are intrinsic to the NESS and reflect a generalized rigidity.
5pp, 2 figs, final version incl supplemental material