Compression of Kitaev quantum spin liquid candidate Na₃Co₂SbO₆ to megabar pressures

A direct outcome of Kitaev's work on his exactly solvable model for quantum spin liquids (QSLs) was the intensified search for materials that would realize this magnetically frustrated state, in particular due to the rising of fractionalized excitations with potential application in the field of quantum computing. One compound that has recently been the focal point of study for several theoretical and experimental groups around the world is Na₃Co₂SbO₆ (NCSO), in particular after it was predicted that NCSO could stabilize a QSL state under hydrostatic compression or uniaxial strain. Therefore, in this work we studied NCSO phases under extreme conditions by the means of multiple synchrotron spectroscopic and diffraction techniques, as well as by measuring its macroscopic properties. Upon compression, NCSO maintains its ambient-pressure atomic structure and shows increased ferromagnetic correlations up to about 70 GPa; while higher pressures drive a high-spin-low-spin transition on Co²⁺ ions that destroys the J_eff -1/2 state needed to stabilize the Kitaev QSL phase. However, this pressure-tuned set of localized, low-spin Co moments may still give rise to frustrated magnetism, showing that honeycomb lattices of cobaltates present a fertile platform for exploring novel magnetic quantum states.