Thermal conductance in a spin-boson model: Cotunneling and low temperature properties

TL;DR

This paper investigates bosonic thermal transport in a two-level system at low temperatures, revealing cotunneling processes and deriving an analytic description of the crossover from sequential to cotunneling regimes, with anomalous scaling behavior.

Contribution

It provides a detailed analytic analysis of low-temperature thermal conductance in a spin-boson model, highlighting cotunneling effects and scaling properties.

Findings

Transport is dominated by two-boson cotunneling at low temperatures.

An analytic description of the sequential-cotunneling crossover is developed.

Low-temperature thermal conductance exhibits anomalous scaling behavior.

Abstract

Bosonic thermal transport through a two-level system is analyzed at temperatures below and comparable to the two-level energy splitting. It is shown that in the low-temperature regime transport is dominated by correlated two-boson processes analogous to electron cotunneling in quantum dots under Coulomb blockade. We present a detailed analysis of the sequential-cotunneling crossover and obtain essentially an analytic description of the transport problem. Perturbative analysis is complemented by employing scaling properties of the Ohmic spin-boson model, allowing us to extract an anomalous low temperature scaling of thermal conductance.