Pressure-induced dimerization and valence bond crystal formation in the Kitaev-Heisenberg magnet alpha-RuCl3

TL;DR

This study demonstrates that applying pressure to alpha-RuCl3 induces a structural and magnetic phase transition, leading to dimerization and valence bond crystal formation, which competes with the Kitaev spin liquid phase.

Contribution

The paper reveals a pressure-induced transition in alpha-RuCl3, showing how structural changes promote valence bond solid formation over the Kitaev spin liquid.

Findings

Pressure causes a triclinic phase with Ru-Ru dimerization.

Magnetic susceptibility collapses at the transition.

Enhanced Ru-Ru bonding increases antiferromagnetic interactions.

Abstract

Magnetization and high-resolution x-ray diffraction measurements of the Kitaev-Heisenberg material alpha-RuCl3 reveal a pressure-induced crystallographic and magnetic phase transition at a hydrostatic pressure of p=0.2 GPa. This structural transition into a triclinic phase is characterized by a very strong dimerization of the Ru-Ru bonds, accompanied by a collapse of the magnetic susceptibility. Ab initio quantum-chemistry calculations disclose a pressure-induced enhancement of the direct 4d-4d bonding on particular Ru-Ru links, causing a sharp increase of the antiferromagnetic exchange interactions. These combined experimental and computational data show that the Kitaev spin liquid phase in alpha-RuCl3 strongly competes with the crystallization of spin singlets into a valence bond solid.