26 research outputs found
Voltage profile and four terminal resistance of an interacting quantum wire
We investigate the behavior of the four-terminal resistance in a
quantum wire described by a Luttinger liquid in two relevant situations: (i) in
the presence of a single impurity within the wire and (ii) under the effect of
asymmetries introduced by dirty voltage probes. In the first case, interactions
leave a signature in a power law behavior of as a function of the
voltage and the temperature . In the second case interactions tend to
mask the effect of the asymmetries. In both scenarios the occurrence of
negative values of is explained in simple terms.Comment: 5 pages, 3 figures; added references, corrected typos, improved
explanation
Effect of nonadiabatic switching of dynamic perturbations in 1d Fermi systems
We study a two-dimensional fermionic QFT used to model 1D strongly correlated
electrons in the presence of a time-dependent impurity that drives the system
out of equilibrium. In contrast to previous investigations, we consider a
dynamic barrier switched on at a finite time. We compute the total energy
density (TED) of the system and establish two well defined regimes in terms of
the relationship between the frequency of the time-dependent perturbation
and the electron energy . Finally, we derive a relaxation time
such that for times shorter than the finite-time switching
process is relevant.Comment: 9 pages, 4 figures. Changed title. Added comments on backscattering.
Added result for electrical current. Version accepted in PR
An alternative formulation of classical electromagnetic duality
By introducing a doublet of electromagnetic four dimensional vector
potentials, we set up a manifestly Lorentz covariant and SO(2) duality
invariant classical field theory of electric and magnetic charges. In our
formulation one does not need to introduce the concept of Dirac string.Comment: 14 pages, no figures, Latex, minor corrections, references and
acknowledgements adde
Non local Thirring model with backward and umklapp interactions
We extend a non local and non covariant version of the Thirring model in
order to describe a many-body system with backward and umklapp scattering
processes. We express the vacuum to vacuum functional in terms of a non trivial
fermionic determinant. Using path-integral methods we find a bosonic
representation for this determinant which allows us to obtain an effective
action for the collective excitations of the system. By introducing a non local
version of the self-consistent harmonic approximation, we get an expression for
the gap of the charge-density excitations as functional of arbitrary
electron-electron potentials. As an example we also consider the case of a non
contact umklapp interaction.Comment: 19 pages, no figure
Non-perturbative approach to backscattering off a dynamical impurity in 1D Fermi systems
We investigate the problem of backscattering off a time-dependent impurity in
a one-dimensional electron gas. By combining the Schwinger-Keldysh method with
an adiabatic approximation in order to deal with the corresponding out of
equilibrium Dirac equation, we compute the total energy density (TED) of the
system. We show how the free fermion TED is distorted by the backscattering
amplitude and the geometry of the impurity.Comment: 5 pages, 2 figures, RevTex4. Appendix and some text added. Results
and conclusions did not change. Version accepted for publication in Phys.
Rev.
Functional bosonization with time dependent perturbations
We extend a path-integral approach to bosonization previously developed in
the framework of equilibrium Quantum Field Theories, to the case in which
time-dependent interactions are taken into account. In particular we consider a
non covariant version of the Thirring model in the presence of a dynamic
barrier at zero temperature. By using the Closed Time Path (Schwinger-Keldysh)
formalism, we compute the Green's function and the Total Energy Density of the
system. Since our model contains the Tomonaga Luttinger model as a particular
case, we make contact with recent results on non-equilibrium electronic
systems.Comment: 21 pages, 8 figure
RG study of a non local sine-Gordon model
We study a non local version of the sine-Gordon model connected to a
many-body system with backward and umklapp scattering processes. Using
renormalization group methods we derive the flow equations for the couplings
and show how non locality affects the gap in the spectrum of charge-density
excitations. We compare our results with previous predictions obtained through
the self-consistent harmonic approximation.Comment: 15 pages, 4 figures. Revised version, accepted for publication in
Nuclear Physics
Improved harmonic approximation and the 2D Ising model at and
We propose a new method to determine the unknown parameter associated to a
self-consistent harmonic approximation. We check the validity of our technique
in the context of the sine-Gordon model. As a non trivial application we
consider the scaling regime of the 2D Ising model away from the critical point
and in the presence of a magnetic field . We derive an expression that
relates the approximate correlation length , and .Comment: 11 pages, Latex, 3 figures. Accepted for publication in Journal of
Physics
Transient effects in the backscattered current of a Luttinger liquid
We study the backscattered current in a Luttinger liquid in the presence of a
point like weak impurity switched on at finite time, taking into account
finite-temperature effects. We show how the well-known results for a static
impurity are distorted. We derive a dimensionless parameter as
function of the electron-electron interaction and the temperature, such that
for ) the switching process is relevant (irrelevant). Our
results suggest the possibility of determining the value of the Luttinger
parameter through time measurements in transport experiments at fixed
voltage.Comment: 8 pages, 3 figures. To appear in Physical Review