Dimensional reduction and incommensurate dynamic correlations in the $S=\frac{1}{2}$ triangular-lattice antiferromagnet Ca$_3$ReO$_5$Cl$_2$

TL;DR

This study reveals that Ca$_3$ReO$_5$Cl$_2$, a triangular-lattice antiferromagnet, exhibits quasi-1D magnetic correlations due to frustration, with Dzyaloshinskii-Moriya interactions shifting the spinon continuum and opening a zero-field gap.

Contribution

The paper demonstrates how Dzyaloshinskii-Moriya interactions influence spin dynamics and induce a gap in a frustrated triangular-lattice antiferromagnet, supported by high-field ESR and magnetization data.

Findings

Quasi-1D magnetic correlations observed despite 2D structure

Dzyaloshinskii-Moriya interaction shifts spinon continuum in momentum space

Zero-field gap at the $B3$ point directly observed

Abstract

The observation of spinon excitations in the $S=\frac{1}{2}$ triangular antiferromagnet Ca$_3$ReO$_5$Cl$_2$ reveals a quasi-one-dimensional (1D) nature of magnetic correlations, in spite of the nominally 2D magnetic structure. This phenomenon is known as frustration-induced dimensional reduction. Here, we present high-field electron spin resonance spectroscopy and magnetization studies of Ca$_3$ReO$_5$Cl$_2$, allowing us not only to refine spin-Hamiltonian parameters, but also to investigate peculiarities of its low-energy spin dynamics. We argue that the presence of the uniform Dzyaloshinskii-Moriya interaction (DMI) shifts the spinon continuum in momentum space and, as a result, opens a zero-field gap at the $\Gamma$ point. We observed this gap directly. The shift is found to be consistent with the structural modulation in the ordered state, suggesting this material as a perfect model triangular-lattice system, where a pure DMI-spiral ground state can be realized.