Heat transport and rectification in the quantum Rabi model

Abstract: 

The Nakajima-Zwanzig approach to open quantum systems is applied to steady-state bosonic transport in multilevel junctions. Approximate expressions are provided up to fourth order in the system-bath coupling. These generalize to multilevel systems the known results for the low-temperature thermal conductance in the spin-boson model [1]. With this formalism we study the problem of heat transport in a qubit-resonator junction described by the quantum Rabi model. Nontrivial transport features emerge as a result of the interplay between the qubit-oscillator detuning and coupling strength [2]. For quasi-degenerate spectra, nonvanishing steady-state coherences cause a suppression of the heat current. The qubit-resonator system is nonlinear and couples asymmetrically to the heat baths. As a result, the heat current depends on the direction of the temperature bias, i.e. the Rabi model displays rectification. We study how the latter is affected by the qubit-resonator coupling and detuning, and by the presence of steady-state coherences.

[1] L. Magazzù, E. Paladino, M. Grifoni, Phys. Rev. B 110 (8), 085419 (2024)

[2] L. Magazzù, E. Paladino, M. Grifoni, arXiv:2403.06909 (2024)