7,353 research outputs found
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
Topological phase transition based on the attractive Hubbard model
We theoretically investigate the effect of an attractive on-site interaction
on the two-band magnetic Dirac fermion model based on a square lattice system.
When the attractive fermion interaction is taken into account by the mean-field
approximation, a phase diagram is obtained. It is found that a quantum phase
transition from a band insulator state to quantum anomalous Hall state occurs
with increased attractive interaction. For an existing quantum anomalous Hall
state, the attractive interaction enlarges its nontrivial band gap and makes
the topological edge states more localized, which protects the transport of
linear-dispersive edge states against finite-size and further disorder effects.Comment: 5 pages, 4 figure
- …