Temperature-Dependent Three-Dimensional Anisotropy of the Magnetoresistance in WTe2

Extremely large magnetoresistance (XMR) was recently discovered in WTe2, triggering extensive research on this material regarding the XMR origin. Since WTe2 is a layered compound with metal layers sandwiched between adjacent insulating chalcogenide layers, this material has been considered to be electronically two-dimensional (2D). Here we report two new findings on WTe2 : (1) WTe2 is electronically 3D with a mass anisotropy as low as 2, as revealed by the 3D scaling behavior of the resistance R(H,theta) = R(epsilon H-theta) with epsilon(theta) = (cos(2)theta + gamma(-2)sin(2)theta)(1/2), theta being the magnetic field angle with respect to the c axis of the crystal and. being the mass anisotropy and (2) the mass anisotropy gamma varies with temperature and follows the magnetoresistance behavior of the Fermi liquid state. Our results not only provide a general scaling approach for the anisotropic magnetoresistance but also are crucial for correctly understanding the electronic properties of WTe2, including the origin of the remarkable turn-on behavior in the resistance versus temperature curve, which has been widely observed in many materials and assumed to be a metalinsulator transition.