Odd-even layer-number effect of valence-band spin splitting in 
<math>
  <msub>
    <mi>WTe</mi>
    <mn>2</mn>
  </msub>
</math>

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

doi:10.1103/physrevresearch.4.023247

Journal article Odd-even layer-number effect of valence-band spin splitting in ${WTe}_{2}$

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Masato Sakano, Yuma Tanaka, Satoru Masubuchi, Shota Okazaki, Takuya Nomoto, Atsushi Oshima, Kenji Watanabe, Takashi Taniguchi, Ryotaro Arita, Takao Sasagawa, Tomoki Machida, Kyoko Ishizaka. Odd-even layer-number effect of valence-band spin splitting in

{WTe}_{2}

. Physical Review Research. 2022, 4 (2), 023247. https://doi.org/10.1103/physrevresearch.4.023247

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When a crystal becomes thinner and thinner to the atomic level, peculiar phenomena discretely depending on its layer-numbers (n) start to appear. The symmetry and wave functions strongly reflect the layer-numbers and stacking order, which brings us a potential of realizing new properties and functions that is unexpected in either bulk or simple monolayer. Multilayer WTe2 is one such example exhibiting unique ferroelectricity and non-linear transport properties related to the antiphase stacking and Berry-curvature dipole. Here we investigate the electronic band dispersions of multilayer WTe2 (2-5 layers), by performing laser-based micro-focused angle-resolved photoelectron spectroscopy on exfoliated-flakes that are strictly sorted by n and encapsulated by graphene. We clearly observed the insulator-semimetal transition occurring between 2 and 3-layers, 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.

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