Superconductor-metal quantum transition at the EuO-KTaO3 interface

TL;DR

This paper investigates the superconductor-metal quantum phase transition at the EuO-KTaO3 interface, revealing quantum Griffiths singularity and providing insights into exotic superconducting states at oxide interfaces.

Contribution

It presents the first experimental study of the quantum phase transition and Griffiths singularity at the EuO/KTaO3 interface, highlighting disorder effects on superconductivity.

Findings

Divergence of dynamical critical exponent observed.

Evidence of quantum Griffiths singularity at the interface.

Large rare superconducting regions and disorder influence the transition.

Abstract

Superconductivity has been one of the most fascinating quantum states of matter for over several decades. Among the superconducting materials, LaAlO3/SrTiO3 interface is of particularly interest since superconductivity exists between two insulating materials, which provides it with various unique applications compared with bulk superconductors and makes it a suitable platform to study the quantum Hall effect, charge density wave, superconductivity and magnetism in one device. Therefore, a lot of efforts have been made to search new superconducting oxide interface states with higher superconducting critical temperature (TC). Recently, a superconducting state with TC ~ 2 K has been found at the interface between a ferromagnetic insulator EuO and a band insulator (111)-KTaO3. Here, we report the experimental investigation of the superconductor-metal quantum phase transition of the EuO/KTaO3 interface. Around the transition, a divergence of the dynamical critical exponent is observed, which supports the quantum Griffiths singularity in the EuO/KTaO3 interface. The quantum Griffiths singularity could be attributed to large rare superconducting regions and quenched disorders at the interface. Our results could pave the way for studying the exotic superconducting properties at the EuO/KTaO3 interface.