Electrically controlled superconductor-insulator transition and giant anomalous Hall effect in kagome metal CsV3Sb5 nanoflakes

TL;DR

This study demonstrates electrical control over the superconductor-insulator transition and giant anomalous Hall effect in kagome CsV3Sb5 nanoflakes, revealing disorder-driven phase changes and their relation to charge order and topological properties.

Contribution

It introduces a protonic gating method to modulate electronic states and uncovers a disorder-driven superconductor-insulator transition in CsV3Sb5 nanoflakes.

Findings

Superconductor-insulator transition driven by phase fluctuations.

Significant suppression of charge density wave (CDW).

Evolution of anomalous Hall effect linked to Fermi level shifts.

Abstract

The electronic correlations (e.g. unconventional superconductivity (SC), chiral charge order and nematic order) and giant anomalous Hall effect (AHE) in topological kagome metals AV3Sb5 (A= K, Rb, and Cs) have attracted great interest. Electrical control of those correlated electronic states and AHE allows us to resolve their own nature and origin and to discover new quantum phenomena. Here, we show that a protonic gate can largely modulate the effective disorders and carrier density in CsV3Sb5 nanoflakes, leading to significant modifications of SC, unusual charge density wave (CDW) and giant AHE. Notably, we observed a direct superconductor-insulator transition (SIT) driven by superconducting phase fluctuation due to the doping-enhanced disorders, in addition to a large suppression of CDW. Meanwhile, the carrier density modulation shifts the Fermi level across the CDW gap and gives rise to a nontrivial evolution of AHE, in line with the asymmetric density of states of CDW sub-bands near the saddle point. With the first-principles calculations, we suggest the extrinsic skew scattering of holes in the nearly flat bands with finite Berry curvature by multiple impurities accounts for the giant AHE. Our work uncovers a disorder-driven bosonic SIT, outlines a global picture of the giant AHE and reveals its correlation with the unconventional CDW in the AV3Sb5 family.