Strong modulation of carrier effective mass in WTe2 via coherent lattice manipulation
The layered transition-metal dichalcogenide WTe2 is characterized by distinctive transport and topological properties. These emergent electronic properties can in principle be manipulated by changes in the crystal structure. However, how precisely a given structural change alters the electronic properties is typically difficult to determine, as direct structural probes with high time resolution are required. A team of researchers working at the Bernina beamline of SwissFEL has now followed the structural dynamics in WTe2 after excitation with femtosecond laser pulses, with particular focus on coherent phonon modes. Their time-resolved X-ray diffraction results, supported by infrared reflectivity measurements, suggest that phonons might periodically modulate the effective mass of carriers in the electron and hole pockets by up to 20% — indicating a route to controlling the peculiar transport properties of WTe2 on short time scales.