Extremely large magnetoresistance in the type-II Weyl semimetal Mo Te 2

We performed the angle dependent magnetoresistance (MR), Hall effect measurements, the temperature dependent magneto-thermoelectric power (TEP) $S$($T$) measurements, and the first-principles calculations to study the electronic properties of orthorhombic phase $\mathrm{Mo}{\mathrm{Te}}_{2}\phantom{\rule{0.28em}{0ex}}({T}_{d}\ensuremath{-}\mathrm{Mo}{\mathrm{Te}}_{2})$, which was proposed to be electronically two dimensional (2D). There are some interesting findings about ${T}_{d}\ensuremath{-}\mathrm{Mo}{\mathrm{Te}}_{2}$. (1) A scaling approach ${\ensuremath{\varepsilon}}_{\ensuremath{\theta}}={(\mathrm{si}{\mathrm{n}}^{2}\ensuremath{\theta}+{\ensuremath{\gamma}}^{\ensuremath{-}2}\mathrm{co}{\mathrm{s}}^{2}\ensuremath{\theta})}^{1/2}$ is applied, where $\ensuremath{\theta}$ is the magnetic field angle with respect to the $c$ axis of the crystal and $\ensuremath{\gamma}$ is the mass anisotropy. Unexpectedly, the electronically three-dimensional (3D) character with $\ensuremath{\gamma}$ as low as 1.9 is observed in ${T}_{d}\ensuremath{-}\mathrm{Mo}{\mathrm{Te}}_{2}$. (2) The possible Lifshitz transition and the following electronic structure change can be verified around $T\ensuremath{\sim}150\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and $T\ensuremath{\sim}60\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, which is supported by the evidence of the slope changing of the temperature dependence of TEP, the carrier density extracted from Hall resistivity, and the onset temperature of $\ensuremath{\gamma}$ obtained from the MR measurements. The extremely large MR effect in ${T}_{d}\ensuremath{-}\mathrm{Mo}{\mathrm{Te}}_{2}$ could originate from the combination of the electron-hole compensation and a particular orbital texture on the electron pocket, which is supported by the calculations of electronic structure. Our results may provide a general scaling relation for the anisotropic MR and help to recognize the origins of the MR effect in other systems, such as the Weyl semimetals and the Dirac ones.