Pressure tuning of competing interactions on a honeycomb lattice

TL;DR

This study demonstrates how applying pressure to a honeycomb lattice material can tune magnetic interactions, suppress magnetic ordering, and approach a quantum critical point without structural dimerization, revealing insights into spin liquid behavior.

Contribution

It provides experimental and theoretical evidence that pressure modifies bond angles to tune the ratio of Kitaev to Heisenberg interactions, approaching a quantum critical point in Ag3LiRh2O6.

Findings

Pressure suppresses the Neel temperature in Ag3LiRh2O6.

Pressure increases the |K/J| ratio, favoring spin liquid behavior.

The material approaches a quantum critical point without structural dimerization.

Abstract

Magnetic exchange interactions are mediated via orbital overlaps across chemical bonds. Thus, modifying the bond angles by physical pressure or strain can tune the relative strength of competing interactions. Here we present a remarkable case of such tuning between the Heisenberg (J) and Kitaev (K) exchange, which respectively establish magnetically ordered and spin liquid phases on a honeycomb lattice. We observe a rapid suppression of the Neel temperature (TN) with pressure in Ag3LiRh2O6, a spin-1/2 honeycomb lattice with both J and K couplings. Using a combined analysis of x-ray data and first-principles calculations, we find that pressure modifies the bond angles in a way that increases the |K/J| ratio and thereby suppresses TN. Consistent with this picture, we observe a spontaneous onset of muon spin relaxation (muSR) oscillations below TN at low pressure, whereas in the high-pressure phase, oscillations appear only when T < TN/2. Unlike other candidate Kitaev materials, Ag3LiRh2O6 is tuned toward a quantum critical point by pressure while avoiding a structural dimerization in the relevant pressure range.