Anisotropic Straintronic Transport in Topological Semimetal Nanoflakes

Strain engineering is not only a powerful tool to enhance the functional properties of quantum materials for practical applications but also a unique technique to uncover the underlying mechanisms dictating those properties. One of the most promising systems for strain engineering is two-dimensional materials, such as transition metal dichalcogenide (TMD) thin layers, which have large mechanical strength and highly sensitive electronic and optical properties. Most of the previous experimental studies have focused on semiconducting TMDs by tuning their band gap and electrical properties at room temperature. Here, we report for the first time low-temperature, strain-dependent magneto-transport studies of semimetal WTe 2 nanoflake devices. By applying a uniaxial tensile strain along two crystallographic directions ( a - and b -axes), we have observed a clear anisotropic elastoresistivity, where the resistivity has opposite responses to the applied strain in the two directions. The electron density extracted from the magnetoresistance and Hall measurements decreases as a function of the tensile strain along the a -axis and increases along the b -axis. The anisotropic strain-dependence of the transport properties is understood based on the density functional theory calculations of the electronic band structures and Fermi surfaces. Our work experimentally demonstrates strain as an effective tool to tune the low-temperature transport properties of nanostructured topological metals for straintronic applications.