Defining the effective temperature of a quantum driven system from current-current correlation functions

Abstract

We calculate current-current correlation functions and find an expression for the zero-frequency noise of multiterminal systems driven by harmonically time-dependent voltages within the Keldysh nonequilibrium Green's functions formalism. We also propose a fluctuation-dissipation relation for currentcurrent correlation functions to define an effective temperature.We discuss the behavior of this temperature and compare it with the local temperature determined by a thermometer and with the effective temperature defined from a single-particle fluctuation-dissipation relation. We show that for low frequencies all the definitions of the temperature coincide. © Springer-Verlag 2012.