Discovery of a new phase in thin flakes of KV$_{3}$Sb$_{5}$ under pressure

TL;DR

This study uncovers a new pressure-induced phase in KV$_{3}$Sb$_{5}$ thin flakes, revealing complex phase interactions without Fermi surface reconstruction, through magnetotransport, Hall effect, quantum oscillations, and theoretical analysis.

Contribution

It reports the discovery of a previously unidentified phase boundary in KV$_{3}$Sb$_{5}$ under pressure, expanding understanding of its phase diagram and electronic structure.

Findings

Identification of a new phase boundary $T^{\ast}(p)$ under pressure.

The new phase does not alter the Fermi surface topology.

The phase diagram includes charge-density-wave and superconducting transitions.

Abstract

We report results of magnetotransport measurements on KV$_3$Sb$_5$ thin flakes under pressure. Our zero-field electrical resistance reveals an additional anomaly emerging under pressure ($p$), marking a previously unidentified phase boundary $T^{\rm \ast}$($p$). Together with the established $T_{\rm CDW}(p)$ and $T_c(p)$, denoting the charge-density-wave transition and a superconducting transition, respectively, the temperature-pressure phase diagram of KV$_3$Sb$_5$ features a rich interplay among multiple phases. The Hall coefficient evolves reasonably smoothly when crossing the $T^{\rm \ast}$ phase boundary compared with the variation when crossing $T_{\rm CDW}$, indicating the preservation of the pristine electronic structure. The mobility spectrum analysis provides further insights into distinguishing different phases. Finally, our high-pressure quantum oscillation studies up to 31 T combined with density functional theory calculations further demonstrate that the new phase does not reconstruct the Fermi surface, confirming that the translational symmetry of the pristine metallic state is preserved.