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TT: Fachverband Tiefe Temperaturen
TT 19: Quantum Coherence (joint session TT/DY)
TT 19.5: Talk
Monday, March 18, 2024, 17:30–17:45, H 3025
Diagrammatic approach to quantum heat transport in the quantum Rabi model — •Luca Magazzu1, Elisabetta Paladino2, 3, and Milena Grifoni1 — 1University of Regensburg — 2Università di Catania, Italy — 3INFN, Sez. Catania, Italy
A diagrammatic approach to quantum transport in Liouville space, valid for bosonic/fermionic environments, is applied to bosonic heat transport in the quantum Rabi model. Heat transport at weak interaction with the heat baths is controlled by the qubit-oscillator coupling g. Universality of the linear conductance versus the temperature is found below a coupling-dependent Kondo-like temperature.
At low temperature, coherent 4th-order processes dominate transport yielding a T3 behavior for the thermal conductance κ. In the high-temperature regime, incoherent emission/absorption processes constitute the main transport mechanism, giving resonant peaks, at low g, when the qubit frequency matches the one of the oscillator. In these conditions, the spectrum of the Rabi model displays quasi-degeneracies that produce non-vanishing coherences at the steady state which, in turn, impact κ.
In moving from the weak to the ultrastrong qubit-oscillator coupling regime, the low-T conductance converges to the one of an effective two-level system. At high T, κ makes a transition from a resonant peak to a broad, zero-bias peak regime, a behavior that parallels the one found for the spin-boson model at strong qubit-bath coupling.
Keywords: Quantum heat transport; Quantum Rabi model; Diagrammatic approach; Coherent processes; Ultrastrong coupling