We investigate the behavior of the four-terminal resistance R 4pt in a quantum wire described by a Luttinger liquid in two relevant situations: ͑i͒ in the presence of a single impurity within the wire and ͑ii͒ under the effect of asymmetries introduced by disordered 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.
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.
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