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We report the quantum transport properties of Cd3As3 single crystals in a magnetic field. A large linear quantum magnetoresistance is observed near room temperature. With decreasing temperature, the Shubnikov--de Haas oscillations appear in both the longitudinal resistance Rxx and the transverse Hall resistance Rxy. From the strong oscillatory component ARxx, a linear dependence of the Landau index n on 1/5 is obtained, and it gives an n-axis intercept between 1/2 and 5/8. This clearly reveals a nontrivial n Berry's phase, which is a distinguished feature of Dirac fermions. Our quantum transport results provide bulk evidence for the existence of a three-dimensional Dirac semimetal phase in Cd3As2. [ABSTRACT FROM AUTHOR]

The quantum oscillations of the magnetoresistance under ambient and high pressure have been studied for WTe2 single crystals, in which extremely large magnetoresistance was discovered recently. By analyzing the Shubnikov-de Haas oscillations, four Fermi surfaces are identified, and two of them are found to persist to high pressure. The sizes of these two pockets are comparable, but show increasing difference with pressure. At 0.3 K and in 14.5 T, the magnetoresistance decreases drastically from 1.25 × 105% under ambient pressure to 7.47 × 103% under 23.6 kbar, which is likely caused by the relative change of Fermi surfaces. These results support the scenario that the perfect balance between the electron and hole populations is the origin of the extremely large magnetoresistance in WTe2. [ABSTRACT FROM AUTHOR]

We present the ultralow-temperature specific heat and thermal conductivity measurements on single crystals of YbMgGaO4, 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 (Cm ~ T0.74). 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 Cm 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. [ABSTRACT FROM AUTHOR]