Quantum heat transport in a spin-boson nanojunction: Coherent and incoherent mechanisms

Department of Physics and State Key Laboratory of Surface Physics, Fudan University - Shanghai 200433, China

^(a) cqw@fudan.edu.cn

Received: 4 March 2014
Accepted: 10 July 2014

Abstract

Quantum heat transport in a spin-boson system under nonequilibrium steady state (NESS) is investigated by the nonequilibrium Green's function (NEGF) method. Spin-spin correlators are calculated via the Majorana fermion representation of spin operators, which allows us to make use of Wick's theorem through standard diagrammatic techniques. An analytic formula of heat current is obtained, and numerical results are presented in comparison with those obtained by other methods. Two types of transport mechanisms are identified in high- and low-temperature regions, respectively, which shows a transition from incoherent to coherent transport process with the baths' temperatures decreased. Additionally, a saturation of the heat current is confirmed when increasing the coupling strength between the baths and the intermediate system, which is a sign of quantum Zeno effect (QZE) in the transport process.