On the multi-$\mathbf{q}$ characteristics of magnetic ground states of honeycomb cobalt oxides

TL;DR

This paper reviews the complex multi-q magnetic ground states in honeycomb cobalt oxides, highlighting experimental methods, crystallographic symmetries, and implications for quantum magnetic models, challenging the traditional single-q magnetic order assumption.

Contribution

It provides a comprehensive review of experimental strategies and crystallographic considerations for identifying multi-q magnetic orders in honeycomb cobalt oxides, advancing understanding of their magnetic ground states.

Findings

Evidence for multi-q zigzag order in Na₂Co₂TeO₆ and Na₃Co₂SbO₆

Comparison of experimental strategies for distinguishing magnetic orders

Discussion on the formation mechanisms of multi-q order

Abstract

The Kitaev honeycomb model has received significant attention for its exactly solvable quantum spin liquid ground states and fractionalized excitations. For realizing the model, layered cobalt oxides have been considered a promising platform. Yet, in contrast to the conventional wisdom about single-$\mathbf{q}$ zigzag magnetic order inferred from previous studies of the Na$_2$IrO$_3$ and $\alpha$-RuCl$_3$ candidate materials, recent experiments on two of the representative honeycomb cobalt oxides, hexagonal Na$_2$Co$_2$TeO$_6$ and monoclinic Na$_3$Co$_2$SbO$_6$, have uncovered evidence for more complex multi-$\mathbf{q}$ variants of the zigzag order. This review surveys on experimental strategies to distinguish between single- and multi-$\mathbf{q}$ orders, along with the crystallographic symmetries of the cobalt oxides in comparison to the previously studied systems. General formation mechanism of multi-$\mathbf{q}$ order is also briefly discussed. The goal is to provide some rationales for examining the relevance of multi-$\mathbf{q}$ order in the honeycomb cobalt oxides, along with its implications on the microscopic model of these intriguing quantum magnets.