Odd-even layer-number effect of valence-band spin splitting in WTe2

Authors
Masato Sakano, Yuma Tanaka, Satoru Masubuchi, Shota Okazaki, Takuya Nomoto, Atsushi Oshima, Kenji Watanabe, Takashi Taniguchi, Ryotaro Arita, Takao Sasagawa, Tomoki Machida, and Kyoko Ishizaka

Abstract
When a crystal becomes thin to the atomic level, peculiar phenomena discretely depending on its layer numbers (n) start to appear. Here, we investigate the electronic band dispersions of multilayer WTe₂ (2–5 layers), by performing laser-based microfocused angle-resolved photoelectron spectroscopy on exfoliated flakes sorted by n. We observe that the holelike valence bands start to cross the Fermi level when the number of layers is increased from 2- to 3 layers, which should be related to the insulator-semimetal transition, as well as the 30–70-meV spin splitting of valence bands manifesting in even n as a signature of stronger structural asymmetry. Our result fully demonstrates the possibility of the large energy-scale band and spin manipulation through the finite-n stacking procedure.

Physical Review Research: https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.4.023247