On the temperature dependence of ballistic Coulomb drag in nanowires

We have investigated within the theory of Fermi liquid dependence of Coulomb drag current in a passive quantum wire on the applied voltage $V$ across an active wire and on the temperature $T$ for any values of $eV/k_BT$. We assume that the bottoms of the 1D minibands in both wires almost coincide with the Fermi level. We come to conclusions that 1) within a certain temperature interval the drag current can be a descending function of the temperature $T$; 2) the experimentally observed temperature dependence $T^{-0.77}$ of the drag current can be interpreted within the framework of Fermi liquid theory; 3) at relatively high applied voltages the drag current as a function of the applied voltage saturates; 4) the screening of the electron potential by metallic gate electrodes can be of importance.Comment: 7 pages, 1 figur

Low temperature electron-phonon resonance in dc-current-biased two-dimensional electron systems

Effects of resonant acoustic phonon scattering on magnetoresistivity are examined in two-dimensional electron systems at low temperatures by using a balance-equation magnetotransport scheme direct controlled by the current. The experimentally observed resonances in linear resistivity are shown to result from the conventional bulk phonon modes in a GaAs-based system, without invoking leaky interface phonons. Due to quick heating of electrons, phonon resonances can be dramatically enhanced by a finite bias current. When the electron drift velocity increases to the speed of sound, additional and prominent phonon resonance peaks begin to emerge. As a result, remarkable resistance oscillation and negative differential resistivity can appear in nonlinear transport in a modest mobility sample at low temperatures, which is in agreement with recent experiments.Comment: 7 pages, 5 figures, published versio

Low Field Magnetic Response of the Granular Superconductor LaSrCuO

The properties of the low excitation field magnetic response of the granular high temperature (HTSC) superconductor LaSrCuO have been analyzed at low temperatures. The response of the Josephson currents has been extracted from the data. It is shown that intergrain current response is fully irreversible, producing shielding response, but do not carry Meissner magnetization. Analysis of the data shows that the system of Josephson currents freezes into a glassy state even in the absense of external magnetic field, which is argued to be a consequence of the d-wave nature of superconductivity in LaSrCuO. The macroscopic diamagnetic response to very weak variations of the magnetic field is shown to be strongly irreversible but still qualitatively different from any previously known kind of the critical-state behaviour in superconductors. A phenomenological description of these data is given in terms of a newly proposed ``fractal'' model of irreversibility in superconductors.Comment: LATEX, twocolumns, 22 pages including 20 eps-figure