Chemical tuning of a honeycomb magnet through a critical point

TL;DR

This study demonstrates how chemical substitution in BaCo2(AsO4)2 tunes its magnetic ground state, revealing a critical point that may facilitate the realization of a quantum spin liquid.

Contribution

It identifies a critical substitution level where magnetic interactions balance, leading to a complex ground state possibly stabilized by quantum fluctuations.

Findings

Suppression of long-range order at 3.0 K with arsenic to vanadium substitution.

Increased spin freezing at higher substitution levels.

A critical point at around 10% substitution where magnetic interactions balance.

Abstract

BaCo2(AsO4)2 (BCAO) has seen extensive study since its initial identification as a proximate Kitaev quantum spin liquid candidate. Thought to be described by the highly anisotropic XXZ-J_1-J_3 model, the ease with which magnetic order is suppressed in the system indicates proximity to a spin liquid phase. Upon chemical tuning via partial arsenic substitution with vanadium, we show an initial suppression of long-range incommensurate order in the BCAO system to T = 3.0 K, followed by increased spin freezing at higher substitution levels. Between these two regions, at around 10% substitution, the system is shown to pass through a critical point where the competing J_1/J_3 exchange interactions become more balanced, producing a more complex magnetic ground state, likely stabilized by quantum fluctuations. This state shows how slight compositional change in magnetically-frustrated systems may be leveraged to tune ground state degeneracies and potentially realize a quantum spin liquid state.