Xu Y, Zhang J, Li Y S, Yu Y J, Hong X C, Zhang Q M, Li S Y
State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China.
Department of Physics, Renmin University of China, Beijing 100872, China.
Phys Rev Lett. 2016 Dec 23;117(26):267202. doi: 10.1103/PhysRevLett.117.267202.
We present the ultralow-temperature specific heat and thermal conductivity measurements on single crystals of YbMgGaO_{4}, which was recently argued to be a promising candidate for a quantum spin liquid (QSL). In a zero magnetic field, a large magnetic contribution of specific heat is observed, and exhibits a power-law temperature dependence (C_{m}∼T^{0.74}). On the contrary, we do not observe any significant contribution of thermal conductivity from magnetic excitations. In magnetic fields H≥6 T, the exponential T dependence of C_{m} and the enhanced thermal conductivity indicate a magnon gap of the fully polarized state. The absence of magnetic thermal conductivity at the zero field in this QSL candidate puts a strong constraint on the theories of its ground state.
我们展示了对YbMgGaO₄单晶的超低温比热和热导率测量结果，YbMgGaO₄最近被认为是量子自旋液体（QSL）的一个有前景的候选材料。在零磁场中，观察到比热有很大的磁贡献，并呈现出幂律温度依赖性（Cm∼T⁰.⁷⁴）。相反，我们没有观察到磁激发对热导率有任何显著贡献。在磁场H≥6 T时，Cm的指数T依赖性和增强的热导率表明了完全极化态的磁振子能隙。在这个QSL候选材料的零场中不存在磁热导率，这对其基态理论施加了很强的限制。
