Cooper Pair Writing at the LaAlO3/SrTiO3 Interface

TL;DR

This study demonstrates the formation of Cooper pairs and quantum phase transitions at the LaAlO3/SrTiO3 interface using low-temperature magnetotransport, revealing complex superconducting behaviors and potential for electronic phase control.

Contribution

It shows that conductive structures at the LaAlO3/SrTiO3 interface can exhibit superconducting, metallic, and insulating phases at low temperatures, with evidence of Cooper pair formation and quantum phase transitions.

Findings

Observation of a quantum phase transition related to Cooper pairs.

Presence of Shubnikov-de Haas oscillations at high mobility interfaces.

Finite resistance persists even at the lowest temperatures.

Abstract

The LaAlO3/SrTiO3 interface provides a unique platform for controlling the electronic properties of the superconducting semiconductor SrTiO3. Prior investigations have shown that two-dimensional superconductivity can be produced at the LaAlO3/SrTiO3 interface and tuned electrostatically. The recently demonstrated reversible control of the metal-insulator transition at the same interface using conductive atomic force microscopy (c-AFM) raises the question of whether this room-temperature technique can produce structures that exhibit superconducting, normal metallic and insulating phases at sub-Kelvin temperatures. Here we report low-temperature magnetotransport experiments on conducting structures defined at an otherwise insulating LaAlO3/SrTiO3 interface. A quantum phase transition associated with the formation of Cooper pairs is observed in these predefined structures at sub-Kelvin temperatures. However, a finite resistance remains even at the lowest temperature. At higher magnetic fields, interfaces with high mobility also exhibit strong Shubnikov-de Haas oscillations as well as a larger Ginsburg-Landau coherence length. Cooper pair localization, spin-orbit coupling, and finite-size effects may factor into an explanation for some of the unusual properties observed.