In two-dimensional (2D) limit, the quantum fluctuation is significantly enhanced which could induce a quantum phase transition. Investigating the quantum criticality is an effective approach to elucidate the underlying physics of 2D superconductivity. Here we report the observation of different universality classes of quantum criticality at the superconducting LaAlO3/KTaO3 (111) interface, i.e. the normal quantum Griffiths singularity (QGS) and the anomalous QGS. The switch of the quantum criticality class is observed from the normal QGS in a low Tc sample with weaker spin-orbit coupling (SOC) to the anomalous QGS in a high Tc sample with stronger SOC. Moreover, owing to the remarkable SOC strength, the high Tc sample exhibits an unprecedentedly enhanced quantum fluctuation at an unusually elevated temperature approaching the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature TBKT. This work provides comprehensive recognition of the different quantum criticality classes in the same superconducting LaAlO3/KTaO3 (111) system, which deepens the understanding of the superconducting mechanism of interfacial superconductors.
@article{arxiv.2410.19668,
title = {Observation of Quantum-Criticality-Class Crossover at the LaAlO$_3$/KTaO$_3$ (111) Interface},
author = {Jia Liu and Long Cheng and Mingyue Zhang and Junkun Zha and Fei Ye and Xiaofang Zhai},
journal= {arXiv preprint arXiv:2410.19668},
year = {2025}
}