Static magnetic order with strong quantum fluctuations in spin-1/2 honeycomb magnet Na2Co2TeO6

TL;DR

This study investigates Na2Co2TeO6, revealing strong quantum fluctuations and frustrated interactions that may lead to a quantum-spin-liquid state, using neutron scattering and muon-spin techniques.

Contribution

It provides new experimental insights into the magnetic properties and quantum fluctuations in Na2Co2TeO6, a candidate Kitaev material, highlighting the robustness of quantum effects under magnetic fields.

Findings

Muon-spin relaxation rate remains constant below TN, indicating strong quantum fluctuations.

Neutron scattering shows a broader spin-wave gap at the K-point with increasing magnetic field.

Quantum fluctuations are enhanced by applied magnetic fields.

Abstract

Kitaev interactions, arising from the interplay of frustration and bond anisotropy, can lead to strong quantum fluctuations and, in an ideal case, to a quantum-spin-liquid state. However, in many nonideal materials, spurious non-Kitaev interactions typically promote a zigzag antiferromagnetic order in the d-orbital transition metal compounds. By combining neutron scattering with muon-spin rotation and relaxation techniques, we provide new insights into the exotic properties of Na2Co2TeO6, a candidate Kitaev material. Below TN, the zero-field muon-spin relaxation rate becomes almost constant (at 0.45 us-1). We attribute this temperature-independent muon-spin relaxation rate to the strong quantum fluctuations, as well as to the frustrated Kitaev interactions. As the magnetic field increases, neutron scattering data indicate a much broader spin-wave-excitation gap at the K-point. Therefore, quantum fluctuations seem not only robust, but are even enhanced by the applied magnetic field. Our findings provide valuable hints for understanding the onset of the quantum-spin-liquid state in Kitaev materials.