Carrier density independent scattering rate in SrTiO3-based electron liquids

TL;DR

This study reveals that in SrTiO3-based electron liquids, the scattering rate remains constant regardless of carrier density, challenging traditional Fermi liquid theory and suggesting a broader need for new theoretical frameworks.

Contribution

It demonstrates carrier density independence of scattering rates in SrTiO3 electron liquids, contrasting with Fermi liquid predictions and linking to non-Fermi liquid behaviors in correlated materials.

Findings

Scattering rate is independent of carrier density.

Behavior resembles non-Fermi liquids like cuprates.

Questions the applicability of Fermi liquid theory.

Abstract

We examine the carrier density dependence of the scattering rate in two- and three-dimensional electron liquids in SrTiO3 in the regime where it scales with T^n (T is the temperature and n <= 2) in the cases when it is varied by electrostatic control and chemical doping, respectively. It is shown that the scattering rate is independent of the carrier density. This is contrary to the expectations from Landau Fermi liquid theory, where the scattering rate scales inversely with the Fermi energy (E_F). We discuss that the behavior is very similar to systems traditionally identified as non-Fermi liquids (n < 2). This includes the cuprates and other transition metal oxide perovskites, where strikingly similar density-independent scattering rates have been observed. The results indicate that the applicability of Fermi liquid theory should be questioned for a much broader range of correlated materials and point to the need for a unified theory.