11 research outputs found
Real-time path integral approach to nonequilibrium many-body quantum system
A real-time path integral Monte Carlo approach is developed to study the
dynamics in a many-body quantum system until reaching a nonequilibrium
stationary state. The approach is based on augmenting an exact reduced equation
for the evolution of the system in the interaction picture which is amenable to
an efficient path integral (worldline) Monte Carlo approach. Results obtained
for a model of inelastic tunneling spectroscopy reveal the applicability of the
approach to a wide range of physically important regimes, including high
(classical) and low (quantum) temperatures, and weak (perturbative) and strong
electron-phonon couplings.Comment: 5 pages, 2 figure
Local density of states on a vibrational quantum dot out of equilibrium
We calculate the nonequilibrium local density of states on a vibrational
quantum dot coupled to two electrodes at T=0 using a numerically exact
diagrammatic Monte Carlo method. Our focus is on the interplay between the
electron-phonon interaction strength and the bias voltage. We find that the
spectral density exhibits a significant voltage dependence if the voltage
window includes one or more phonon sidebands. A comparison with
well-established approximate approaches indicates that this effect could be
attributed to the nonequilibrium distribution of the phonons. Moreover, we
discuss the long transient dynamics caused by the electron-phonon coupling.Comment: 9 pages, 11 figure
Dissipative Dynamics with Trapping in Dimers
The trapping of excitations in systems coupled to an environment allows to
study the quantum to classical crossover by different means. We show how to
combine the phenomenological description by a non-hermitian Liouville-von
Neumann Equation (LvNE) approach with the numerically exact path integral
Monte-Carlo (PIMC) method, and exemplify our results for a system of two
coupled two-level systems. By varying the strength of the coupling to the
environment we are able to estimate the parameter range in which the LvNE
approach yields satisfactory results. Moreover, by matching the PIMC results
with the LvNE calculations we have a powerful tool to extrapolate the
numerically exact PIMC method to long times.Comment: 5 pages, 2 figure
Long transient dynamics in the Anderson-Holstein model out of equilibrium
We calculate the time dependent nonequilibrium current through a single level
quantum dot strongly coupled to a vibrational mode. The nonequilibrium real
time dynamics caused by an instantaneous coupling of the leads to the quantum
dot is discussed using an approximate method. The approach, which is specially
designed for the strong polaronic regime, is based on the so-called polaron
tunneling approximation. Considering different initial dot occupations, we show
that a common steady state is reached after times much larger than the typical
electron tunneling times due to a polaron blocking effect in the dot charge. A
direct comparison is made with numerically exact data, showing good agreement
for the time scales accessible by the diagrammatic Monte Carlo simulation
method