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.