Cumulants of heat transfer across nonlinear quantum systems

Abstract

We consider thermal conduction across a general nonlinear phononic junction. Based on two time observation protocol and the nonequilibrium Green's function method, heat transfer in steady state regimes is studied, and practical formulas for the calculation of the cumulant generating function are obtained. As an application, the general formalism is used to study anharmonic effects on fluctuation of steady state heat transfer across a single site junction with a quartic nonlinear on site pinning potential. An explicit nonlinear modification to the cumulant generating function exact up to the first order is given, in which the Gallavotti Cohen fluctuation symmetry is found still valid. Numerically a self consistent procedure is introduced, which works well for strong nonlinearity.©EDP Sciences, Societ̀a Italiana di Fisica, Springer Verlag 2013.