On a CFT prediction in the sine-Gordon model

A quantitative prediction of Conformal Field Theory (CFT), which relates the second moment of the energy-density correlator away from criticality to the value of the central charge, is verified in the sine-Gordon model. By exploiting the boson-fermion duality of two-dimensional field theories, this result also allows to show the validity of the prediction in the strong coupling regime of the Thirring model.Comment: 5 pages, no figures, late

Voltage profile and four terminal resistance of an interacting quantum wire

We investigate the behavior of the four-terminal resistance $R_{4pt}$ 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 $R_{4pt}$ as a function of the voltage $V$ and the temperature $T$. In the second case interactions tend to mask the effect of the asymmetries. In both scenarios the occurrence of negative values of $R_{4pt}$ is explained in simple terms.Comment: 5 pages, 3 figures; added references, corrected typos, improved explanation

Quantum pump effect in one-dimensional systems of Dirac fermions

We investigate the behavior of the directed current in one-dimensional systems of Dirac fermions driven by local periodic potentials in the forward as well in backscattering channels. We treat the problem with Keldysh non-equilibrium Green's function formalism. We present the exact solution for the case of an infinite wire and show that in this case the dc current vanishes identically. We also investigate a confined system consistent in an annular arrangement coupled to a particle reservoir. We present a perturbative treatment that allows for the analytical expressions of the dc current in the lowest order of the amplitudes of the potential. We also present results obtained from the exact numerical solution of the problem.Comment: 8 pages, 5 figure

Backscattering off a dynamical impurity in one-dimensional Fermi systems: a perturbative computation

We investigate the problem of backscattering off a time-dependent and spatially extended barrier in a one-dimensional noninteracting electron gas. By performing a perturbative expansion in the backscattering amplitude, we compute the total energy density of the system. We show how the free fermion spectrum and the conductance of the system are affected by the interplay between dynamical and geometrical properties of the impurity.Instituto de Física La Plat

Transient and finite-size effects in transport properties of a quantum wire

We study the time-dependent backscattered current produced in a quantum wire when a local barrier is suddenly switched on. Previous investigations are improved by taking into account the finite length of the device. We establish two different regimes in terms of the relationship between the energy scales associated with the voltage and the length of the system. We show how previous results, valid for wires of infinite length, are modified by the finite size of the system. In particular, our study reveals a rich pattern of temporal steps within which the current suffers an initial relaxation followed by temporary revivals. By employing both analytical and numerical methods we describe peculiar features of this structure. From this analysis one concludes that our results render a recently proposed approach to the determination of the Luttinger parameter, K, more realistic.Facultad de Ciencias ExactasInstituto de Física La Plat

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 $\Omega$ and the electron energy $\omega$. Finally, we derive a relaxation time $t_{R}$ such that for times shorter than $t_{R}$ 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

Backscattering off a dynamical impurity in one-dimensional Fermi systems: a perturbative computation

We investigate the problem of backscattering off a time-dependent and spatially extended barrier in a one-dimensional noninteracting electron gas. By performing a perturbative expansion in the backscattering amplitude, we compute the total energy density of the system. We show how the free fermion spectrum and the conductance of the system are affected by the interplay between dynamical and geometrical properties of the impurity.Instituto de Física La Plat

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.Facultad de Ciencias ExactasInstituto de Física La Plat

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