Transition to an Insulating Phase Induced by Attractive Interactions in the Disordered Three-Dimensional Hubbard Model

We study numerically the interplay of disorder and attractive interactions for spin-1/2 fermions in the three-dimensional Hubbard model. The results obtained by projector quantum Monte Carlo simulations show that at moderate disorder, increasing the attractive interaction leads to a transition from delocalized superconducting states to the insulating phase of localized pairs. This transition takes place well within the metallic phase of the single-particle Anderson model.Comment: revtex, 4 pages, 3 figure

Conductivity of 2D many-component electron gas, partially-quantized by magnetic field

The 2D semimetal consisting of heavy holes and light electrons is studied. The consideration is based on assumption that electrons are quantized by magnetic field while holes remain classical. We assume also that the interaction between components is weak and the conversion between components is absent. The kinetic equation for holes colliding with quantized electrons is utilized. It has been stated that the inter-component friction and corresponding correction to the dissipative conductivity $\sigma_{xx}$ {\it do not vanish at zero temperature} due to degeneracy of the Landau levels. This correction arises when the Fermi level crosses the Landau level. The limits of kinetic equation applicability were found. We also study the situation of kinetic memory when particles repeatedly return to the points of their meeting.Comment: 13 pages, 1 figur

Influence of temperature gradients on tunnel junction thermometry below 1 K: cooling and electron-phonon coupling

We have studied thermal gradients in thin Cu and AlMn wires, both experimentally and theoretically. In the experiments, the wires were Joule heated non-uniformly at sub-Kelvin temperatures, and the resulting temperature gradients were measured using normal metal-insulator-superconducting tunnel junctions. The data clearly shows that even in reasonably well conducting thin wires with a short ($\sim 10 \mu$m) non-heated portion, significant temperature differences can form. In most cases, the measurements agree well with a model which includes electron-phonon interaction and electronic thermal conductivity by the Wiedemann-Franz law.Comment: J. Low Temp. Phys. in pres

Disordered Hubbard Model with Attraction: Coupling Energy of Cooper Pairs in Small Clusters

We generalize the Cooper problem to the case of many interacting particles in the vicinity of the Fermi level in the presence of disorder. On the basis of this approach we study numerically the variation of the pair coupling energy in small clusters as a function of disorder. We show that the Cooper pair energy is strongly enhanced by disorder, which at the same time leads to the localization of pairs.Comment: revtex, 5 pages, 6 figure

Temperature dependent resistivity of spin-split subbands in GaAs 2D hole system

We calculate the temperature dependent resistivity in spin-split subbands induced by the inversion asymmetry of the confining potential in GaAs 2D hole systems. By considering both temperature dependent multisubband screening of impurity disorder and hole-hole scattering we find that the strength of the metallic behavior depends on the symmetry of the confining potential (i.e., spin-splitting) over a large range of hole density. At low density above the metal-insulator transition we find that effective disorder reduces the enhancement of the metallic behavior induced by spin-splitting. Our theory is in good qualitative agreement with existing experiments

DISSIPATIVE CONDUCTIVITY DETERMINED BY CARRIER-CARRIER COLLISIONS

On étudie les effets des collisions entre des porteurs sur la conductibilité. La dissipation existe suivant deux cas : i) le courant est continu, sans le champ magnétique, dans un système de porteurs compensés, c'est-à-dire avec la charge totale égale à zéro ; ii) le courant est alternatif dans un champ magnétique ou sans, dans un système de porteurs différant de e/m.Carrier-Carrier collisions may lead to the dissipative conductivity in two cases : under dc conditions without magnetic field in a compensated system, i.e. in one with total charge of the carriers equal to zero ; under ac conditions both with the magnetic field and without it, when the carriers of the system have different e/m ratios

DISSIPATIVE CONDUCTIVITY DETERMINED BY CARRIER-CARRIER COLLISIONS

On étudie les effets des collisions entre des porteurs sur la conductibilité. La dissipation existe suivant deux cas : i) le courant est continu, sans le champ magnétique, dans un système de porteurs compensés, c'est-à-dire avec la charge totale égale à zéro ; ii) le courant est alternatif dans un champ magnétique ou sans, dans un système de porteurs différant de e/m.Carrier-Carrier collisions may lead to the dissipative conductivity in two cases : under dc conditions without magnetic field in a compensated system, i.e. in one with total charge of the carriers equal to zero ; under ac conditions both with the magnetic field and without it, when the carriers of the system have different e/m ratios

Positive curvature in the temperature dependence of H-c2 in KxBa1-xBiO3

Contains fulltext : 29377.pdf (publisher's version ) (Open Access