Complete miscibility amongst AV$_3$Sb$_5$ kagome superconductors: design of mixed A-site AV$_3$Sb$_5$ (A: K, Rb, Cs) alloys

TL;DR

This study demonstrates complete miscibility in AV$_3$Sb$_5$ kagome superconductors through A-site alloying, mapping electronic instabilities and revealing continuous property trends across the alloy compositions.

Contribution

It provides the first comprehensive phase diagram showing full miscibility and continuous electronic property evolution in mixed A-site AV$_3$Sb$_5$ alloys.

Findings

Full miscibility of alkali-site elements in AV$_3$Sb$_5$

Continuous variation of $T_ ext{CDW}$ and $T_ ext{c}$ with composition

Enhanced CDW stability in K$_{1-x}$Cs$_{x}$V$_3$Sb$_5$ alloys

Abstract

In this work we explore the chemical-property phase diagram of the AV$_3$Sb$_5$ family through A-site alloying. We demonstrate full miscibility of the alkali-site, highlighting that the three parent compounds are the terminal ends of a single solid-solution. Using both polycrystalline and single crystal methods, we map the dependence of the two primary electronic instabilities: (1) the onset of charge density wave (CDW) order ($T_\text{CDW}$) and (2) the onset of superconductivity ($T_\text{c}$) with alkali-site composition. We show continuous trends in both $T_\text{CDW}$ and $T_\text{c}$, including a region of enhanced CDW stability in K$_{1-x}$Cs$_{x}$V$_3$Sb$_5$ alloys. Together, our results open new routes for chemical perturbation and exploration of the chemical-property relationships in the class of AV$_3$Sb$_5$ kagome superconductors.