4 research outputs found
Electron-electron interaction effects in quantum point contacts
We consider electron-electron interaction effects in quantum point contacts on the first quantization plateau, taking into account all scattering processes. We compute the low-temperature linear and nonlinear conductance, shot noise, and thermopower, by perturbation theory and a self-consistent nonperturbative method. On the conductance plateau, the low-temperature corrections are solely due to momentum-nonconserving processes that change the relative number of left- and right-moving electrons. This leads to a suppression of the conductance for increasing temperature or voltage. The size of the suppression is estimated for a realistic saddle-point potential, and is largest in the beginning of the conductance plateau. For large magnetic field, interaction effects are strongly suppressed by the Pauli principle, and hence the first spin-split conductance plateau has a much weaker interaction correction. For the nonperturbative calculations, we use a self-consistent nonequilibrium Green's function approach, which suggests that the conductance saturates at elevated temperatures. These results are consistent with many experimental observations related to the so-called 0.7 anomaly
Electronic transport in inhomogeneous quantum wires
We study the transport properties of a long non-uniform quantum wire where
the electron-electron interactions and the density vary smoothly at large
length scales. We show that these inhomogeneities lead to a finite resistivity
of the wire, due to a weak violation of momentum conservation in the collisions
between electrons. Estimating the rate of change of momentum associated with
non-momentum-conserving scattering processes, we derive the expression for the
resistivity of the wire in the regime of weakly interacting electrons and find
a contribution linear in temperature for a broad range of temperatures below
the Fermi energy. By estimating the energy dissipated throughout the wire by
low-energy excitations, we then develop a different method for deriving the
resistivity of the wire, which can be combined with the bosonization formalism.
This allows us to compare our results with previous works relying on an
extension of the Tomonaga-Luttinger model to inhomogeneous systems.Comment: 18 pages, 2 figures. Invited paper for special issue of Journal of
Physics: Condensed Matter on "The 0.7 Feature and Interactions in
One-dimensional Systems