246 research outputs found
The interacting resonant level model in nonequilibrium: finite temperature effects
We study the steady-state properties as well as the relaxation dynamics of
the nonequilibrium interacting resonant level model at finite temperatures. It
constitutes the prototype model of a correlated charge fluctuating quantum dot.
The two reservoirs are held at different chemical potentials---the difference
being the bias voltage---and different temperatures; we discuss the transport
through as well as the occupancy of the single level dot. First, we show
analytically that in the steady state the reservoir temperatures in competition
with the other energy scales act as infrared cutoffs. This is rather intuitive
but, depending on the parameter regime under consideration, leads to a
surprisingly rich variety of power laws in the current as a function of the
temperatures and the bias voltage with different interaction dependent
exponents. Next we clarify how finite reservoir temperatures affect the
dynamics. They allow to tune the interplay of the two frequencies
characterizing the oscillatory part of the time evolution of the model at zero
temperature. For the exponentially decaying part we disentangle the
contributions of the level-lead hybridization and the temperatures to the decay
rates. We identify a coherent-to-incoherent transition in the long time
dynamics as the temperature is raised. It occurs at an interaction dependent
critical temperature. Finally, taking different temperatures in the reservoirs
we discuss the relaxation dynamics of a temperature gradient driven current.Comment: 12 pages, 6 figures, 1 tabl
Entanglement scaling of excited states in large one-dimensional many-body localized systems
We study the properties of excited states in one-dimensional many-body
localized (MBL) systems using a matrix product state algorithm. First, the
method is tested for a large disordered non-interacting system, where for
comparison we compute a quasi-exact reference solution via a Monte Carlo
sampling of the single-particle levels. Thereafter, we present extensive data
obtained for large interacting systems of L~100 sites and large bond dimensions
chi~1700, which allows us to quantitatively analyze the scaling behavior of the
entanglement S in the system. The MBL phase is characterized by a logarithmic
growth (L)~log(L) over a large scale separating the regimes where volume and
area laws hold. We check the validity of the eigenstate thermalization
hypothesis. Our results are consistent with the existence of a mobility edge
Efficiency and power of a thermoelectric quantum dot device
We study linear response and nonequilibrium steady-state thermoelectric
transport through a single-level quantum dot tunnel coupled to two reservoirs
held at different temperatures as well as chemical potentials. A fermion
occupying the dot interacts with those in the reservoirs by a short-ranged
two-particle interaction. For parameters for which particles flow against a
bias voltage from the hot to the cold reservoir this setup acts as an
energy-conversion device with which electrical energy is gained out of waste
heat. We investigate how correlations affect its efficiency and output power.
In linear response the changes in the thermoelectric properties can be traced
back to the interaction induced renormalization of the resonance line shape. In
particular, small to intermediate repulsive interactions reduce the maximum
efficiency. In nonequilibrium the situation is more complex and we identify a
parameter regime in which for a fixed lower bound of the output power the
efficiency increases.Comment: 6 pages, 6 figure
Loschmidt-amplitude wave function spectroscopy and the physics of dynamically driven phase transitions
We introduce the Loschmidt amplitude as a powerful tool to perform spectroscopy of generic many-body wave functions and use it to interrogate the wave function obtained after ramping the transverse field quantum Ising model through its quantum critical point. Previous results are confirmed and a more complete understanding of the population of defects and of the effects of magnon-magnon interaction or finite-size corrections is obtained. The influence of quantum coherence is clarified
Dynamical regimes of dissipative quantum systems
We reveal several distinct regimes of the relaxation dynamics of a small
quantum system coupled to an environment within the plane of the dissipation
strength and the reservoir temperature. This is achieved by discriminating
between coherent dynamics with damped oscillatory behavior on all time scales,
partially coherent behavior being nonmonotonic at intermediate times but
monotonic at large ones, and purely monotonic incoherent decay. Surprisingly,
elevated temperature can render the system `more coherent' by inducing a
transition from the partially coherent to the coherent regime. This provides a
refined view on the relaxation dynamics of open quantum systems.Comment: 5 pages, 3 figure
Spectral properties of one-dimensional Fermi systems after an interaction quench
We show that the single-particle spectral properties of gapless
one-dimensional Fermi systems in the Luttinger liquid state reached at
intermediate times after an abrupt quench of the two-particle interaction are
highly indicative of the unusual nonequilibrium nature of this state. The line
shapes of the momentum integrated and resolved spectral functions strongly
differ from their ground state as well as finite temperature equilibrium
counterparts. Using an energy resolution improved version of radio-frequency
spectroscopy of quasi one-dimensional cold Fermi gases it should be possible to
experimentally identify this nonequilibrium state by its pronounced spectral
signatures.Comment: 5 pages, 3 figure
- …