Sub-Ohmic to super-Ohmic crossover behavior in nonequilibrium quantum systems with electron-phonon interactions

Article

关键词: NEGATIVE DIFFERENTIAL RESISTANCE;    SINGLE-MOLECULE;    TUNNELING SPECTROSCOPY;    JUNCTIONS;    MODEL;    DISSIPATION;    TRANSPORT;    DYNAMICS;    DENSITY;    MOTION;   

DOI  :  10.1103/PhysRevB.92.195143

来源: SCIE

【 摘 要 】

The transition from weakly damped coherent motion to localization in the context of the spin-boson model has been the subject of numerous studies with distinct behavior depending on the form of the phonon-bath spectral density J(omega) alpha omega(s). Sub-Ohmic (s < 1) and Ohmic (s = 1) spectral densities show a clear localization transition at zero temperature and zero bias, while for super-Ohmic (s > 1) spectral densities this transition disappears. In this paper, we consider the influence of the phonon-bath spectral density on the nonequilibrium dynamics of a quantum dot with electron-phonon interactions described by the extended Holstein model. Using the reduced density matrix formalism combined with the multilayer multiconfiguration time-dependent Hartree approach, we investigate the dynamic response, the time scales for relaxation, as well as the existence of multiple long-lived solutions as the system-bath coupling changes from the sub- to the super-Ohmic cases. Bistability is shown to diminish for increasing powers of s similar to the spin-boson case. However, the physical mechanism and the dependence on the model parameters such as the typical bath frequency omega(c) and the polaron shift lambda are rather distinct.

【 授权许可】

Free