Quantum bath effects on nonequilibrium heat transport in model molecular junctions

Abstract

Quantum–classical dynamics simulations enable the study of nonequilibrium heat transport in realistic models of molecules coupled to thermal baths. In these simulations, the initial conditions of the bath degrees of freedom are typically sampled from classical distributions. Herein, we investigate the effects of sampling the initial conditions of the thermal baths from quantum and classical distributions on the steady-state heat current in the nonequilibrium spin-boson model—a prototypical model of a single-molecule junction—in different parameter regimes. For a broad range of parameter regimes considered, we find that the steady-state heat currents are ∼1.3–4.5 times larger with the classical bath sampling than with the quantum bath sampling. Using both types of sampling, the steady-state heat currents exhibit turnovers as a function of the bath reorganization energy, with sharper turnovers in the classical case than in the quantum case and different temperature dependencies of the turnover maxima. As the temperature gap between the hot and cold baths increases, we observe an increasing difference in the steady-state heat currents obtained with the classical and quantum bath sampling. In general, as the bath temperatures are increased, the differences between the results of the classical and quantum bath sampling decrease but remain non-negligible at the high bath temperatures. The differences are attributed to the more pronounced temperature dependence of the classical distribution compared to the quantum one. Moreover, we find that the steady-state fluctuation theorem only holds for this model in the Markovian regime when quantum bath sampling is used. Altogether, our results highlight the importance of quantum bath sampling in quantum–classical dynamics simulations of quantum heat transport.

DECIDE: A Deterministic Mixed Quantum-Classical Dynamics Approach

“…Typically, only a few thousand trajectories are required to obtain converged results, in contrast to several orders of magnitude more trajectories in the case of the stochastic QCLE-based methods; (ii) There is no need to diagonalize the Hamiltonian matrix on-the-fly. DECIDE has demonstrated great promise in solving the QCLE with high accuracy and low computational cost for a number of model systems, including the spin-boson model [40,41], Fenna-Matthews-Olson model [40,41], a three-state photo-induced electron transfer model [40], nonequilibrium spin-boson model [21,22,42], and a quantum battery model [43].…”

Temperature-dependent thermal transport of single molecular junctions from semi-classical Langevin molecular dynamics

“…In this work, we employ a semi-classical Langevin molecular dynamics (SCLMD) method [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] to study the temperature dependent κ of single molecular junctions. The statistical properties of the Langevin thermal baths are treated quantum-mechanically, and the deterministic Hamiltonian dynamics of the system is treated classically.…”

Quantum Thermal Transport Beyond Second Order with the Reaction Coordinate Mapping

“…Furthermore, the NESB model has been studied extensively using perturbative and numerically-exact techniques; a partial list includes Refs. 20,[30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] .…”