Heat due to system-reservoir correlations in thermal equilibrium

Abstract

The heat flow between a quantum system and its reservoir is analyzed when initially both are in a separable thermal state and asymptotically approach a correlated equilibrium. General findings are illustrated for specific systems and various classes of non-Markovian reservoirs relevant for solid state realizations. System-bath correlations are shown to be substantial at low temperatures even in the weak coupling regime. As a consequence, predictions of work and heat for actual experiments obtained within conventional perturbative approaches may often be questionable. Correlations induce characteristic imprints in heat capacities which opens a proposal to measure them in solid state devices.

Work and heat for two-level systems in dissipative environments: Strong driving and non-Markovian dynamics

“…A striking feature is the peak in the heat flux at early times, which is present even if there is no driving at all (cf. [18]). We attribute it to the factorizing initial condition (12): The dynamics according to the full Hamiltonian immediately tends to correlate the bath and the system, which in turn is related to heat exchange.…”

“…However, for any finite coupling, the true thermal state is a correlated state of the TLS and the bath, i.e., W β = e −βH (0) /Z, and the corresponding reduced distribution ρ β = Tr R {W β } is not of Gibbs form [18,32]. Accordingly, in actual experiments the true initial state may be only of the form (12) for extremely weak coupling, an issue that will be addressed in more detail below.…”

“…Energy projective measurements of the full compound, including the environmental degrees of freedom, are not feasible, particularly when system degrees of freedom are strongly correlated or even entangled with those of thermal reservoirs. A prominent example that received much attention recently are reservoirs with sub-Ohmic mode distribution [16][17][18].…”

“…In addition, the SLN gives access to the impact of correlations between system and bath in thermal equilibrium. Namely, when one starts from an initially factorized state between system and reservoir, which is the typical assumption in weak-coupling treatments, a heat flux associated with these correlations is induced [18]. We will apply two different 1098-0121/2015/91(22)/224303 (9) 224303-1 ©2015 American Physical Society…”

Dynamics of energy transport and entropy production in ac-driven quantum electron systems

“…Because of the coupling between the central system and the reservoirs this interpretation is quite nontrivial, see, e.g., Refs. [15,16,44,45].…”