Disorder-Enriched Magnetic Excitations in a Heisenberg-Kitaev Quantum Magnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>Na</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>Co</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>TeO</mml:mi></mml:mrow><mml:mrow><mml:mn>6</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>
Li Xiang, Ramesh Dhakal, Mykhaylo Ozerov, Yuxuan Jiang, Banasree S. Mou, Andrew Ozarowski, Qing Huang, Haidong Zhou, Jiyuan Fang, Stephen M. Winter, Zhigang Jiang, Dmitry Smirnov
Abstract
Using optical magnetospectroscopy, we investigate the magnetic excitations of ${\mathrm{Na}}_{2}{\mathrm{Co}}_{2}{\mathrm{TeO}}_{6}$ in a broad magnetic field range ($0\text{ }\text{ }\mathrm{T}\ensuremath{\le}\mathrm{B}\ensuremath{\le}17.5\text{ }\text{ }\mathrm{T}$) at low temperature. Our measurements reveal rich spectra of in-plane magnetic excitations with a surprisingly large number of modes, even in the high-field spin-polarized state. Theoretical calculations find that the Na-occupation disorder in ${\mathrm{Na}}_{2}{\mathrm{Co}}_{2}{\mathrm{TeO}}_{6}$ plays a crucial role in generating these modes. Our Letter demonstrates the necessity to consider disorder in the spin environment in the search for Kitaev quantum spin liquid states in practicable materials.