Clean ballistic quantum point contact in SrTiO$_3$

TL;DR

This paper presents a new method for creating high-mobility, gate-tunable nanostructures in SrTiO$_3$, demonstrating ballistic quantum point contacts with conductance quantization and potential electron pairing signatures.

Contribution

The authors develop a facile approach to pattern high-mobility SrTiO$_3$ nanostructures, enabling observation of ballistic conductance quantization and persistent degeneracy under magnetic fields.

Findings

Demonstration of ballistic constrictions with conductance quantization

Observation of two-fold degeneracy persisting at high magnetic fields

Potential evidence of electron pairing outside superconducting regime

Abstract

Two dimensional electron gases based on SrTiO$_3$ are an intriguing platform for exploring mesoscopic superconductivity combined with spin-orbit coupling, offering electrostatic tunability from insulator to metal to superconductor within a single material. So far, however, quantum effects in SrTiO$_3$ nanostructures have been complicated by disorder. Here we introduce a facile approach to achieving high mobility and patterning gate-tunable structures in SrTiO$_3$, and use it to demonstrate ballistic constrictions with clean normal state conductance quantization. Conductance plateaus show two-fold degeneracy that persists to magnetic fields of at least 5 T - far beyond what one would expect from the $g$-factor extracted at high fields - a potential signature of electron pairing extending outside the superconducting regime.