Observation of Quantum Griffiths Singularity and Ferromagnetism at Superconducting LaAlO3/SrTiO3(110) Interface

TL;DR

This study reveals quantum Griffiths singularity and signs of ferromagnetism at the LaAlO3/SrTiO3(110) interface, highlighting complex quantum phase transitions and coexistence of magnetic phenomena in a two-dimensional electron gas.

Contribution

It provides the first evidence of quantum Griffiths singularity and ferromagnetism at this interface, advancing understanding of quantum phase transitions in oxide heterostructures.

Findings

Diverging dynamic critical exponent near quantum critical point

Observation of hysteretic magnetoresistance indicating ferromagnetism

Superconductor-metal transition driven by magnetic field

Abstract

Diverse phenomena emerge at the interface between band insulators LaAlO3 and SrTiO3, such as superconductivity and ferromagnetism, showing an opportunity for potential applications as well as bringing fundamental research interests. Particularly, the two-dimensional electron gas formed at LaAlO3/SrTiO3 interface offers an appealing platform for quantum phase transition from a superconductor to a weakly localized metal. Here we report the superconductor-metal transition in superconducting two-dimensional electron gas formed at LaAlO3/SrTiO3(110) interface driven by a perpendicular magnetic field. Interestingly, when approaching the quantum critical point, the dynamic critical exponent is not a constant but a diverging value, which is a direct evidence of quantum Griffiths singularity raised from quenched disorder at ultralow temperatures. Furthermore, the hysteretic property of magnetoresistance was firstly observed at LaAlO3/SrTiO3(110) interfaces, which suggests potential coexistence of superconductivity and ferromagnetism.