Dominant Kitaev Interaction and Field-induced Quantum Disordered Phase in the Cobaltate Na$_2$Co$_2$TeO$_6$

TL;DR

This paper investigates Na$_2$Co$_2$TeO$_6$, a promising Kitaev candidate, revealing a field-induced quantum disordered phase and identifying a dominant AFM Kitaev interaction through experimental measurements and theoretical modeling.

Contribution

It introduces an effective spin model for Na$_2$Co$_2$TeO$_6$ that explains the high-field behavior and uncovers an intermediate quantum spin liquid phase, advancing understanding of Kitaev physics in cobaltates.

Findings

Identification of a field-induced quantum disordered phase.

Development of an effective $K$-$J$-$mma$-$mma^{\u00b0}$ model.

Evidence of a dominant AFM Kitaev interaction.

Abstract

The identification of quantum spin liquid phases in Kitaev candidate materials remains a major experimental challenge. Since most Kitaev candidates develop antiferromagnetic (AFM) order at low temperatures, currently there are great interest on the field-induced magnetic disordered phase in these compounds, that are distinct from (partially) polarized states. Recently, a cobaltate Na$_2$Co$_2$TeO$_6$ has emerged as a promising Kitaev candidate with high-spin $t^{5}_{2g}e^2_g$ configuration and spin-orbit entangled $J_{\rm eff} = 1/2$ honeycomb lattice system. There are intensive studies on field-induced magnetic states and phase transitions under in-plane magnetic fields. In this study, we propose an intermediate disordered phase induced by an out-of-plane field along the $c$-axis, through high-field magnetization and magnetocaloric effect measurements. To explain the high-field behavior of Na$_2$Co$_2$TeO$_6$, we develop an effective $K$-$J$-$\Gamma$-$\Gamma^{\prime}$ spin model featuring a dominant AFM Kitaev interaction. This framework uncovers an intermediate quantum spin liquid phase, establishing the material as a unique platform for exploring Kitaev physics and field-induced quantum-disordered states.