Two phase transitions driven by surface electron doping in WTe2

WTe2 is a multifunctional quantum material exhibiting numerous emergent phases in which tuning of the carrier density plays an important role. Here, we demonstrate two nonmonotonic changes in the electronic structure of WTe2 upon in situ electron doping. The first phase transition is interpreted in terms of a shear displacement of the top WTe2 layer, which realizes a local crystal structure not normally found in bulk WTe2. The second phase transition is associated with stronger interactions between the dopant atoms and the host, both through hybridization and electric field. These results demonstrate that electron doping can drive structural and electronics changes in bulk WTe2 with implications for realizing nontrivial band-structure changes in heterointerfaces and devices.