Nonequilibrium Energy Transfer at Nanoscale: A Unified Theory from Weak to Strong Coupling

We investigate the microscopic mechanism of quantum energy transfer in the nonequilibrium spin-boson model. By developing a nonequilibrium polaron-transformed Redfield equation based on fluctuation decoupling, we dissect the energy transfer into multi-boson associated processes with even or odd parity. Based on this, we analytically evaluate the energy flux, which smoothly bridges the transfer dynamics from the weak spin-boson coupling regime to the strong-coupling one. Our analysis explains previous limiting predictions and provides a unified interpretation of several observations, including coherence-enhanced heat flux and absence of negative differential thermal conductance in the nonequilibrium spin-boson model. The results may find wide applications for the energy and information control in nanodevices.Comment: 11 pages, 4 figure

Rectifying full-counting statistics in a spin Seebeck engine

We investigate the rectification and negative differential effects of full-counting statistics of conjugate thermal spin transport in a spin Seebeck engine. The engine is made by an electron/magnon interface diode driven by a temperature bias, of which the scaled cumulant generating function is formulated in the framework of nonequilibrium Green's function. The strongly fluctuating interfacial electron density of states induced by quantum dot is responsible for these intriguing properties. This work is relevant for designing efficient spin caloritronic engine and can broaden our view in nonequilibrium thermodynamics and the nonlinear phenomenon in quantum transport system.Comment: 10 pages, 4 figure

Probing Noncommutativities of Phase Space by Using Persistent Charged Current and Its Asymmetry

We study the physical properties of the persistent charged current in a metal ring on a noncommutative phase space, and temperature dependence of the noncommutative corrections are also analyzed. We find that the coordinate noncommutativity only affects the total magnitude of the current, and it is difficult to observe it. In contrast, the momentum noncommutativity can violate symmetry property of the current, and this violation of symmetry holds at a finite temperature. Based on this violation effect, we introduce an asymmetry observable to measure the momentum noncommutativity.Comment: 15 pages, 3 figures. v2: typos and a sign in Eq.(5) are corrected, a figure is revised correspondingly; v3: texts are improved, and references are adde