Pressure-dependent Electronic Superlattice in the Kagome-Superconductor CsV$_3$Sb$_5$

TL;DR

This study reveals how pressure induces a transformation in the electronic superlattice of the kagome superconductor CsV$_3$Sb$_5$, correlating with superconducting transition temperature peaks and challenging existing theoretical models.

Contribution

It provides the first high-resolution x-ray diffraction evidence of pressure-induced changes in the superlattice structure of CsV$_3$Sb$_5$, linking these to superconductivity.

Findings

Superlattice transforms from 2x2 to a long-range modulation at 0.7 GPa.

Superconducting T_c peaks correlate with superlattice variations.

Findings challenge ab initio and Peierls nesting models.

Abstract

We present a high-resolution single crystal x-ray diffraction study of kagome-superconductor \cvs, exploring its response to variations in pressure and temperature. We discover that at low temperatures, the structural modulations of the electronic superlattice, commonly associated with charge-density-wave order, undergo a transformation around $p \sim$ 0.7 GPa from the familiar $2\times2$ pattern to a long-range-ordered modulation at wavevector $q=(0, 3/8, 1/2)$. Our observations align with inferred changes in the CDW pattern from prior transport and nuclear-magnetic-resonance studies, providing new insights into these transitions. Interestingly, the pressure-induced variations in the electronic superlattice correlate with two peaks in the superconducting transition temperature as pressure changes, hinting that fluctuations within the electronic superlattice could be key to stabilizing superconductivity. However, our findings contrast with the minimal pressure dependency anticipated by ab initio calculations of the electronic structure. They also challenge prevailing scenarios based on a Peierls-like nesting mechanism involving van Hove singularities.