Disorder induced multifractal superconductivity in monolayer niobium dichalcogenides

TL;DR

This study demonstrates that controlled disorder can enhance superconductivity in monolayer NbSe₂, likely due to multifractality of electron wave functions, providing new insights into disorder effects in quantum materials.

Contribution

It provides the first experimental evidence of disorder-induced multifractal superconductivity in a monolayer material, challenging conventional understanding.

Findings

Superconducting transition temperature increases with disorder in monolayer NbSe₂.

Theoretical modeling suggests multifractality of electron wave functions causes enhancement.

First experimental observation of multifractal superconducting state.

Abstract

The interplay between disorder and superconductivity is a subtle and fascinating phenomenon in quantum many body physics. The conventional superconductors are insensitive to dilute nonmagnetic impurities, known as the Anderson's theorem. Destruction of superconductivity and even superconductor-insulator transitions occur in the regime of strong disorder. Hence disorder-enhanced superconductivity is rare and has only been observed in some alloys or granular states. Because of the entanglement of various effects, the mechanism of enhancement is still under debate. Here we report well-controlled disorder effect in the recently discovered monolayer NbSe$_2$ superconductor. The superconducting transition temperatures of NbSe$_2$ monolayers are substantially increased by disorder. Realistic theoretical modeling shows that the unusual enhancement possibly arises from the multifractality of electron wave functions. This work provides the first experimental evidence of the multifractal superconducting state.