Frustrated charge order and cooperative distortions in ScV6Sn6

TL;DR

This study investigates charge order stability in ScV6Sn6, revealing short-range correlations at high temperatures and long-range order at low temperatures, with frustration effects explained through experimental and theoretical insights.

Contribution

The paper provides experimental validation of the primary lattice instability at q=(1/3,1/3,1/2) and introduces a heuristic model for charge order frustration in ScV6Sn6.

Findings

Charge correlations persist at q=(1/3,1/3,1/2) down to low temperatures.

Long-range order freezes at q=(1/3,1/3,1/3) upon cooling.

Y ion substitution quenches charge correlations.

Abstract

Here we study the stability of charge order in the kagome metal ScV6Sn6. Synchrotron x-ray diffraction measurements reveal high-temperature, short-range charge correlations at the wave vectors along q=(1/3,1/3,1/2) whose inter-layer correlation lengths diverge upon cooling. At the charge order transition, this divergence is interrupted and long-range order freezes in along q=(1/3,1/3,1/3), as previously reported, while disorder enables the charge correlations to persist at the q=(1/3,1/3,1/2) wave vector down to the lowest temperatures measured. Both short-range and long-range charge correlations seemingly arise from the same instability and both are rapidly quenched upon the introduction of larger Y ions onto the Sc sites. Our results validate the theoretical prediction of the primary lattice instability at q=(1/3,1/3,1/2), and we present a heuristic picture for viewing the frustration of charge order in this compound.