15 research outputs found
Non-equilibrium electronic transport in a one-dimensional Mott insulator
We calculate the non-equilibrium electronic transport properties of a
one-dimensional interacting chain at half filling, coupled to non-interacting
leads. The interacting chain is initially in a Mott insulator state that is
driven out of equilibrium by applying a strong bias voltage between the leads.
For bias voltages above a certain threshold we observe the breakdown of the
Mott insulator state and the establishment of a steady-state electronic current
through the system. Based on extensive time-dependent density matrix
renormalization group simulations, we show that this steady-state current
always has the same functional dependence on voltage, independent of the
microscopic details of the model and relate the value of the threshold to the
Lieb-Wu gap. We frame our results in terms of the Landau-Zener dielectric
breakdown picture. Finally, we also discuss the real-time evolution of the
current, and characterize the current-carrying state resulting from the
breakdown of the Mott insulator by computing the double occupancy, the spin
structure factor, and the entanglement entropy.Comment: 12 pages RevTex4, 12 eps figures, as published, minor revision
Numerical method for non-linear steady-state transport in one-dimensional correlated conductors
We present a method for investigating the steady-state transport properties
of one-dimensional correlated quantum systems. Using a procedure based on our
analysis of finite-size effects in a related classical model (LC line) we show
that stationary currents can be obtained from transient currents in finite
systems driven out of equilibrium. The non-equilibrium dynamics of correlated
quantum systems is calculated using the time-evolving block decimation method.
To demonstrate our method we determine the full I-V characteristic of the
spinless fermion model with nearest-neighbour hopping t_H and interaction V_H
using two different setups to generate currents (turning on/off a potential
bias). Our numerical results agree with exact results for non-interacting
fermions (V_H=0). For interacting fermions we find that in the linear regime eV
<< 4t_H the current I is independent from the setup and our numerical data
agree with the predictions of the Luttinger liquid theory combined with the
Bethe Ansatz solution. For larger potentials V the steady-state current depends
on the current-generating setup and as V increases we find a negative
differential conductance with one setup while the currents saturate at finite
values in the other one. Both effects are due to finite renormalized
bandwidths.Comment: published versio
Embedding method for the scattering phase in strongly correlated quantum dots
The embedding method for the calculation of the conductance through
interacting systems connected to single channel leads is generalized to obtain
the full complex transmission amplitude that completely characterizes the
effective scattering matrix of the system at the Fermi energy. We calculate the
transmission amplitude as a function of the gate potential for simple
diamond-shaped lattice models of quantum dots with nearest neighbor
interactions. In our simple models we do not generally observe an interaction
dependent change in the number of zeroes or phase lapses that depend only on
the symmetry properties of the underlying lattice. Strong correlations separate
and reduce the widths of the resonant peaks while preserving the qualitative
properites of the scattering phase.Comment: 11 pages, 3 figures. Proceedings of the Workshop on Advanced
Many-Body and Statistical Methods in Mesoscopic Systems, Constanta, Romania,
June 27th - July 2nd 2011. To appear in Journal of Physics: Conference Serie
2PI nonequilibrium versus transport equations for an ultracold Bose gas
The far-from-equilibrium dynamics of an ultracold, one-dimensional Bose gas
is studied. The focus is set on the comparison between the solutions of fully
dynamical evolution equations derived from the 2PI effective action and their
corresponding kinetic approximation in the form of Boltzmann-type transport
equations. It is shown that during the time evolution of the gas a kinetic
description which includes non-Markovian memory effects in a gradient expansion
becomes valid. The time scale at which this occurs is shown to exceed
significantly the time scale at which the system's evolution enters a
near-equilibrium drift period where a fluctuation dissipation relation is found
to hold and which would seem to be predestined for the kinetic approximation.Comment: 24 pages, 7 figures. References adde