Electrical Observation of the Effective Mass in a Single-Crystal WTe₂ Layer

In order to investigate the effective mass of a single-crystalline WTe₂ layer, we measured the temperature dependence of the Shubnikov-de Haas oscillation. In this method, the magnetoresistance with a perpendicular magnetic field is monitored by changing the temperature from 1.9 K to 6 K. The extracted effective mass of WTe₂ for magnetic fields ranging from 6.8 T to 8.7 T is m* = 0.327m₀ which is almost constant in this range. The theoretical expectation values of m*/m₀ for the valence and the conduction bands are 0.58 and 0.26, respectively; the experimental value of the effective mass is between these two values. Thus, our results clearly show that single-crystalline WTe₂ has both electron- and hole-like pockets that simultaneously contribute to electrical transport in the channel.