title: Absence of Magnetic Thermal Conductivity in the Quantum Spin-Liquid Candidate YbMgGaO_{4}.
abstract: 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.
authors.affiliation: State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China.
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Physics, Renmin University of China, Beijing 100872, China.|Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany.
authors.forename: Y S
authors.initials: YS
authors.lastname: Li
authors.affiliation: State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China.
authors.forename: Y J
authors.initials: YJ
authors.lastname: Yu
authors.affiliation: State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China.
authors.forename: X C
authors.initials: XC
authors.lastname: Hong
authors.affiliation: Department of Physics, Renmin University of China, Beijing 100872, China.|Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.|Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China.
authors.forename: Q M
authors.initials: QM
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China.|Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China.
authors.forename: S Y
authors.initials: SY
authors.lastname: Li