Effects of Electron-Electron and Electron-Phonon Interactions in Weakly Disordered Conductors and Heterostuctures

We investigate quantum corrections to the conductivity due to the interference of electron-electron (electron-phonon) scattering and elastic electron scattering in weakly disordered conductors. The electron-electron interaction results in a negative $T^2 \ln T$-correction in a 3D conductor. In a quasi-two-dimensional conductor, $d < v_F/T$ ($d$ is the thickness, $v_F$ is the Fermi velocity), with 3D electron spectrum this correction is linear in temperature and differs from that for 2D electrons (G. Zala et. al., Phys. Rev.B {\bf 64}, 214204 (2001)) by a numerical factor. In a quasi-one-dimensional conductor, temperature-dependent correction is proportional to $T^2$. The electron interaction via exchange of virtual phonons also gives $T^2$-correction. The contribution of thermal phonons interacting with electrons via the screened deformation potential results in $T^4$-term and via unscreened deformation potential results in $T^2$-term. The interference contributions dominate over pure electron-phonon scattering in a wide temperature range, which extends with increasing disorder.Comment: 6 pages, 2figure

Quantum interference of electrons in Nb_{5-\delta}Te_4 single crystals

The compound $Nb_{5-\delta}Te_4$ ($\delta=0.23$) with quasi-one-dimensional crystal structure undergoes a transition to superconductivity at $T_c$=0.6--0.9 K. Its electronic transport properties in the normal state are studied in the temperature range 1.3--270 K and in magnetic fields up to 11 T. The temperature variation of the resistivity is weak ($<2$) in the investigated temperature range. Nonmonotonic behavior of the resistivity is observed which is characterized by two local maxima at $T\sim$2 K and $\sim$30 K. The temperature dependence of the resistivity is interpreted as an interplay of weak localization, weak antilocalization, and electron-electron interaction effects in the diffusion and the Cooper channel. The temperature dependence of the dephasing time $\tau_\phi$ extracted from the magnetoresistance data is determined by the electron-phonon interaction. The saturation of $\tau_\phi$ in the low-temperature limit correlates with $T_c$ of the individual crystal and is ascribed to the scattering on magnetic impurities.Comment: 8 pages, 6 figure