Polaron master equation approach for non-equilibrium quantum processes
Jianshu Cao, Massachusetts Institute of Technology
Nano-scale systems often display intriguing quantum coherent effects due to system-bath couplings, i.e. polaron effect.[1] To describe these effects in heat, energy, charge transport, we adopt the non-equilibrium polaron-transformed Redfield equation, which bridges smoothly between the Redfield-Bloch equation in the weak coupling limit or non-equilibrium NIBA (non-interacting blip approximation) rate in the strong coupling limit [1,2]. In combination with full-counting statistics, the polaron treatment provides a unified analytical method to calculate the non-equilibrium steady state as well as the fluctuations and noise correlations in the non-equilibrium spin-boson model. [2, 3] The polaron analysis can be further extended to optimize the performance of a model light-harvesting system [4] and to demonstrate the phase modulation due to the Aharonov-Bohm effect [5]. If time allows, I will discuss potential extensions of the polaron approach to other systems of current interest. [6]
1) Non-canonical distribution and non-equilibrium transport beyond weak system-bath coupling regime: A polaron transformation approach. D. Xu and J. Cao, Front. Phys. 11, p1 (2016)
2) Non-equilibrium energy transfer at nanoscale: A unified theory from weak to strong coupling. C. Wang, J. Ren, and J. Cao, Sci. Rep. 5, p11787 (2015)
3) Frequency-dependent current noise in quantum heat transfer with full counting statistics. J. Liu, C. -Y. Hsieh, and J. Cao, JCP 148, p234104 (2018)
4) Polaron effects on the performance of light-harvesting systems: A quantum heat engine perspective. D. Xu, C. Wang, Y. Zhao, and J. Cao, New J. Phys. 18, p023003 (2016)
5) Tuning the Aharonov-Bohm effect with dephasing in non-equilibrium transport. G. Engelhardt and J. Cao, Phys. Rev. B 99 (7), p075436(2019)
6) Discontinuities in driven spin-boson systems due to coherent destruction of tunneling: Breakdown of the Floquet-Gibbs distribution. G. Engelhardt, G. Platero and J. Cao, Phys. Rev. Lett. 123(12), 120602/1-7 (2019).