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 ferroelectric-like 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.