Anomalous Transport in High-Mobility Superconducting SrTiO$_3$ Thin Films

TL;DR

This paper reports on the growth of high-mobility SrTiO$_3$ thin films and investigates their anomalous transport behaviors, including effects of Lifshitz transition, AFD transition, and domain walls on superconductivity and carrier dynamics.

Contribution

It introduces hybrid MBE growth of SrTiO$_3$ films with record mobility and provides new insights into the roles of inter- and intra-band scattering and AFD domain walls in transport and superconductivity.

Findings

Sharp resistivity decrease at Lifshitz transition

Enhanced superconducting transition temperature

Anomalous Hall carrier density behavior

Abstract

The study of subtle effects on transport in semiconductors requires high-quality epitaxial structures with low defect density. Using hybrid molecular beam epitaxy (MBE), SrTiO$_3$ films with low-temperature mobility exceeding 42,000 cm$^2$V$^{-1}$s$^{-1}$ at low carrier density of 3 x 10$^{17}$ cm$^{-3}$ were achieved. A sudden and sharp decrease in residual resistivity accompanied by an enhancement in the superconducting transition temperature were observed across the second Lifshitz transition (LT) where the third band becomes occupied, revealing dominant intra-band scattering. These films further revealed an anomalous behavior in the Hall carrier density as a consequence of the antiferrodistortive (AFD) transition and the temperature-dependence of the Hall scattering factor. Using hybrid MBE growth, phenomenological modeling, temperature-dependent transport measurements, and scanning superconducting quantum interference device imaging, we provide critical insights into the important role of inter- vs intra-band scattering and of AFD domain walls on normal-state and superconducting properties of SrTiO$_3$.