Microscopic mechanisms for the Fermi-liquid behavior of Nb-doped strontium titanate

TL;DR

This paper presents a microscopic theory explaining the Fermi-liquid behavior and superconductivity in Nb-doped strontium titanate, highlighting electron-electron and impurity scattering mechanisms and their agreement with experimental data.

Contribution

It introduces a comprehensive microscopic model accounting for phonon interactions and impurity effects, explaining both Fermi-liquid behavior and superconductivity in SrTiO₃.

Findings

Baber electron-electron scattering explains T² dependence of relaxation rate.

Impurity scattering accounts for residual relaxation at low temperatures.

Effective electron-electron interaction can be attractive, enabling superconductivity.

Abstract

The relaxation rate in Nb-doped strontium titanate involving different scattering channels is investigated theoretically. It is demonstrated that the total relaxation rate in SrTiO_{3} is provided mainly by two mechanisms. The Baber electron-electron scattering with participation of both Coulomb and phonon-mediated electron-electron interactions provides the T^{2}-dependence of the relaxation rate. The scattering on the potential landscape caused by impurities is responsible for the residual relaxation rate at low temperatures. A good agreement with experiment is achieved accounting for all phonon branches in strontium titanate, both the optical and acoustic phonons. It is shown that the effective electron-electron interaction can be attractive in strontium titanate, and provides superconductivity at low temperatures and Fermi-liquid response in a wide range of temperatures. Thus our microscopic model supports the notion that superconductivity and Fermi-liquid properties of n-type SrTiO_{3} have a common origin.