Large Fermi surface in pristine kagome metal CsV$_3$Sb$_5$ and enhanced quasiparticle effective masses

TL;DR

This study maps the Fermi surface of pristine CsV$_3$Sb$_5$ using quantum oscillation measurements under pressure, revealing a large, unreconstructed Fermi surface and enhanced quasiparticle masses near the suppression of charge density wave order.

Contribution

It provides the first direct mapping of the Fermi surface in pristine CsV$_3$Sb$_5$ under pressure, clarifying the electronic structure free from charge density wave reconstruction.

Findings

Large Fermi surface with oscillation frequency up to 8,200 T

Simpler quantum oscillation spectrum in the pristine state

Enhanced quasiparticle effective masses near critical pressure

Abstract

The kagome metal CsV$_3$Sb$_5$ is an ideal platform to study the interplay between topology and electron correlation. To understand the fermiology of CsV$_3$Sb$_5$, intensive quantum oscillation (QO) studies at ambient pressure have been conducted. However, due to the Fermi surface reconstruction by the complicated charge density wave (CDW) order, the QO spectrum is exceedingly complex, hindering a complete understanding of the fermiology. Here, we directly map the Fermi surface of the pristine CsV$_3$Sb$_5$ by measuring Shubnikov-de Haas QOs up to 29 T under pressure, where the CDW order is completely suppressed. The QO spectrum of the pristine CsV$_3$Sb$_5$ is significantly simpler than the one in the CDW phase, and the detected oscillation frequencies agree well with our density functional theory calculations. In particular, a frequency as large as 8,200 T is detected. Pressure-dependent QO studies further reveal a weak but noticeable enhancement of the quasiparticle effective masses on approaching the critical pressure where the CDW order disappears, hinting at the presence of quantum fluctuations. Our high-pressure QO results reveal the large, unreconstructed Fermi surface of CsV$_3$Sb$_5$, paving the way to understanding the parent state of this intriguing metal in which the electrons can be organized into different ordered states.