One-dimensionalization by Geometrical Frustration in the Anisotropic Triangular Lattice of the 5d Quantum Antiferromagnet Ca3ReO5Cl2

TL;DR

This study reveals that the anisotropic triangular lattice in Ca3ReO5Cl2 leads to one-dimensional antiferromagnetic spin chains exhibiting a gapless spin liquid state, driven by geometrical frustration despite the two-dimensional structure.

Contribution

It demonstrates how geometrical frustration induces one-dimensionalization in a 2D ATL antiferromagnet, providing new insights into spin liquid behavior in such systems.

Findings

Evidence of gapless spin liquid in Ca3ReO5Cl2

Effective cancellation of inter-chain couplings at low temperature

Comparison with Cs2CuCl4 highlights unique physics

Abstract

We report on the emergence of antiferromagnetic spin chains from two-dimensionally aligned spins on the anisotropic triangular lattice (ATL) in the insulating calcium rhenium oxychloride Ca3ReO5Cl2. The compound contains Re6+ ions each with one unpaired electron in the dxy orbital, which are arranged to form a spin-1/2 ATL with J'/J ~ 0.32 and J = 41 K, where J and J' are magnetic interactions in and between the chains, respectively. In spite of the apparent two dimensionality, we observe clear evidence of a gapless spin liquid that is characteristic of the spin-1/2 Heisenberg chain. This one-dimensionalization must be caused by geometrical frustration: growing antiferromagnetic correlations in every chain effectively cancel out inter-chain zigzag couplings at low temperature. Ca3ReO5Cl2 provides us with a detailed insight into the interesting physics of the ATL antiferromagnet, especially via comparison with the typical ATL compound Cs2CuCl4.