Observation of Quantum Griffith’s singularity and anomalous metal in LaScO₃/SrTiO₃ heterostructure.

Two-dimensional (2D) disordered superconducting systems in the presence of strong quenched disorder can exhibit the phenomenon called Quantum Griffith's singularity. In this phase, the system cannot maintain long-range order but instead form locally ordered phases called rare regions. Sometimes, the formation of these rare regions changes the critical behavior of superconductor-insulator-transition (SIT) to an Infinite randomness quantum critical point. In our work, we show experimentally that for the quasi-2DEG at the LaScO3/SrTiO3 heterostructures interface, the superconductor-to-insulator phase transition is consistent with quantum Griffith's singularity and is associated with an infinite randomness quantum critical point. The emergence of the anomalous metallic phase in the low-temperature regime cuts off the corresponding Griffith's singularity associated with SIT, and the system deviates from the activated dynamical scaling. These deviations direct us to explore the infinite randomness quantum critical point when the system is in the anomalous metallic state.