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Topological Weyl semimetal WTe₂ is a Van der Waals crystal that gained attention for its large and nonsaturating magnetoresistance, which has been attributed to perfect compensation of electron and hole pockets in the bulk electronic structure. Although, altering the electron hole-balance via electron doping is not predicted to yield a structural phase transition, it is reasonable to expect a different electronic ground state with respect to the compensated system.
Here we show via angle resolved photoemission spectroscopy (ARPES), that surface electron doping in WTe₂ can induce a shear displacement in the top layers, producing a crystal structure locally similar to a polytype typically not encountered in ambient conditions. This phase transition is evidenced by pronounced changes in low-energy surface electronic structure with support from first-principles calculations. A second phase transition at higher doping levels is associated with an interplay between hybridization with dopant bands and Stark effect that affects higher-energy band structure.
[1] Rossi et al., PHYSICAL REVIEW B102, 121110(R) (2020)