Field-induced phase transitions and quantum criticality in the honeycomb antiferromagnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Na</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>Co</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>SbO</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:mrow></mml:math>
Ze Hu, Yue Chen, Yi Cui, Shuo Li, Cong Li, Xiaoyu Xu, Ying Chen, Xintong Li, Yuchen Gu, Rong Yu, Rui Zhou, Yuan Li, Weiqiang Yu
Abstract
We performed $^{23}\mathrm{Na}$ NMR measurements on a single-domain crystal of the Kitaev material ${\mathrm{Na}}_{3}{\mathrm{Co}}_{2}{\mathrm{SbO}}_{6}$ with magnetic field applied along the crystalline $a$ axis. A positive Curie-Weiss constant is obtained from the NMR Knight shift, which suggests the existence of ferromagnetic exchange couplings. The antiferromagnetic ordering is found to be suppressed at a field of 1.9 T. Inside the ordered phase, our data reveal two additional phase transitions. At 1.9 T the spin-lattice relaxation rate $1{/}^{23}{T}_{1}$ establishes a quantum critical behavior at high temperatures. However, at low temperatures a gapped behavior is observed at the ``critical'' field, which suggests a weak first-order transition instead and a possible field-induced quantum spin liquid. Our results reveal complex microscopic interactions in the system that may help to search for possible quantum spin liquids.