Mechanically Tunable Spontaneous Vertical Charge Redistribution in Few-Layer WTe2

Broken symmetry is often the essence of exotic properties in condensed matters. WTe2 exceptionally takes a non-centrosymmetric crystal structure in the family of transition-metal dichalcogenides and exhibits novel properties, such as the nonsaturating magnetoresistance and ferroelectric-like behavior. Herein, using the first-principles calculation, we show that unique layer stacking in WTe2 generates surface dipoles in few-layer WTe2. The surface dipoles are tunable and switchable using the interlayer shear displacement. This could explain the ferroelectriclike behavior recently observed in atomically thin WTe2 films. In addition, we reveal that exfoliation of the surface layer flips the out-of-plane spin textures. The presented results will aid in the deeper understanding, manipulation, and further exploration of the physical properties of WTe2 and related atom-layered materials for applications in electronics and spintronic devices.