The observation of in-plane quantum Griffiths singularity in two-dimensional crystalline superconductors

TL;DR

This study demonstrates the existence of in-plane quantum Griffiths singularity in ultrathin PdTe2 superconducting films under magnetic fields, revealing new insights into disorder effects on quantum phase transitions.

Contribution

It provides the first evidence of quantum Griffiths singularity under parallel magnetic field in 2D crystalline superconductors, using a new scaling analysis.

Findings

QGS appears under both perpendicular and parallel fields in 4-monolayer PdTe2.

QGS disappears under perpendicular field but persists under parallel field in 6-monolayer PdTe2.

The work suggests universality of parallel field induced QGS in 2D superconductors.

Abstract

Quantum Griffiths singularity (QGS) reveals the profound influence of quenched disorder on the quantum phase transitions, characterized by the divergence of the dynamical critical exponent at the boundary of the vortex glass-like phase, named as quantum Griffiths phase. However, in the absence of vortices, whether the QGS can exist under parallel magnetic field remains a puzzle. Here we study the magnetic field induced superconductor-metal transition in ultrathin crystalline PdTe2 films grown by molecular beam epitaxy. Remarkably, the QGS emerges under both perpendicular and parallel magnetic field in 4-monolayer PdTe2 films. The direct activated scaling analysis with a new irrelevant correction has been proposed, providing important evidence of QGS. With increasing film thickness to 6 monolayers, the QGS disappears under perpendicular field but persists under parallel field, and this discordance may originate from the differences in microscopic processes. Our work demonstrates the universality of parallel field induced QGS and can stimulate further investigations on novel quantum phase transitions under parallel magnetic field.