Origin of extremely large magnetoresistance in the candidate type-II Weyl semimetal MoTe_2-x.

ABSTRACT: The recent observation of extremely large magnetoresistance (MR) in the transition-metal dichalcogenide MoTe₂ has attracted considerable interest due to its potential technological applications as well as its relationship with novel electronic states predicted for a candidate type-II Weyl semimetal. In order to understand the origin of the MR, the electronic structure of MoTe_2-x (x?=?0.08) is systematically tuned by application of pressure and probed via its Hall and longitudinal conductivities. With increasing pressure, a monoclinic-to-orthorhombic (1?T' to T_d) structural phase transition temperature (T*) gradually decreases from 210?K at 1?bar to 58?K at 1.1?GPa, and there is no anomaly associated with the phase transition at 1.4?GPa, indicating that a T?=?0?K quantum phase transition occurs at a critical pressure (P_c) between 1.1 and 1.4?GPa. The large MR observed at 1?bar is suppressed with increasing pressure and is almost saturated at 100% for P?>?P_c. The dependence on magnetic field of the Hall and longitudinal conductivities of MoTe_2-x shows that a pair of electron and hole bands are important in the low-pressure T_d phase, while another pair of electron and hole bands are additionally required in the high-pressure 1?T' phase. The MR peaks at a characteristic hole-to-electron concentration ratio (n_c) and is sharply suppressed when the ratio deviates from n_c within the T_d phase. These results establish the comprehensive temperature-pressure phase diagram of MoTe_2-x and underscore that its MR originates from balanced electron-hole carrier concentrations.

SUBMITTER: Lee S 

PROVIDER: S-EPMC6141610 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature