Negative-temperature Fourier transport in one-dimensional systems

We investigate nonequilibrium steady states in a class of one-dimensional diffusive systems that can attain negative absolute temperatures. The cases of a paramagnetic spin system, a Hamiltonian rotator chain and a one-dimensional discrete linear Schrodinger equation are considered. Suitable models of reservoirs are implemented to impose given, possibly negative, temperatures at the chain ends. We show that a phenomenological description in terms of a Fourier law can consistently describe unusual transport regimes where the temperature profiles are entirely or partially in the negative-temperature region. Negative-temperature Fourier transport is observed both for deterministic and stochastic dynamics and it can be generalized to coupled transport when two or more thermodynamic currents flow through the system.

Automated summary

The study focuses on nonequilibrium steady states in a class of one-dimensional diffusive systems capable of reaching negative absolute temperatures. Various systems, including paramagnetic spin systems, Hamiltonian rotator chains, and one-dimensional discrete linear Schrodinger equations, were considered. The research demonstrates that a phenomenological description using a Fourier law can effectively explain unusual transport regimes where temperature profiles exhibit negative-temperature regions. This negative-temperature Fourier transport phenomenon is observed in both deterministic and stochastic dynamics, and can also be extended to coupled transport scenarios with multiple thermodynamic currents.