Polymorph-Tunable Spin Texture and Excitonic Structures in Monolayer WSi2P4
Abstract
Two-dimensional semiconductors that simultaneously possess a direct band gap and strong spin-orbit coupling (SOC) are highly attractive for quantum optoelectronics. Using first-principles GW plus Bethe-Salpeter equation (GW-BSE) calculations, we show that monolayer WSi2P4-an experimentally accessible member of the MSi2X4 family-hosts a direct K-valley gap together with strong SOC. Its three competing polymorphs (alpha, beta and gamma) are all direct-gap semiconductors and are kinetically locked behind 1.3 eV migration barriers. The sigma_h mirror plane of the D3h of alpha and gamma phases enforces a persistent spin texture across the Brillouin zone, weakly modulated near gamma by interband SOC mixing, whereas the polar beta phase (C3v) exhibits Rashba spin splitting. SOC splits the doubly-degenerate lowest bright exciton into dark states and splits the original absorption peak into two peaks (A and B), whose relative brightness is governed by the K-valley conduction-band splitting. alpha-WSi2P4 displays the brightest Peak A because a tiny band crossing of opposite-spin branches can open a spin-allowed radiative channel. These results establish the MSi2P4 family as a phase-tunable platform for the cooperative engineering of spin texture, band splitting, and excitonic brightness within a single material system.
Related
- Influence of nonlocal excitonic optical response on in-plane exciton polaritons supported by monolayer transition-metal dichalcogenides
- Strain-tunable van Hove singularity and superconducting dome in monolayer kagome metal CsTi3Bi5
- Electric-field tunable spin texture in dual-gated HfS2/graphene van der Waals heterostructures
- Electrically tunable moiré hybridization in scalable twist-with-a-spacer structures
- Phase-Tunable Liouvillian Topology: Dual Winding Structures and Skin Effects
BibTeX
@misc{chenwei2026polymorphtunable,
title = {{Polymorph-Tunable Spin Texture and Excitonic Structures in Monolayer WSi2P4}},
author = {Xianbo Chenwei and Yu Zhou and Ke Wu and Gaofeng Xu and Ruixue Li and Yuan Li and Yabei Wu and Shaowen Xu and Fanhao Jia},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.38756},
eprint = {2609.38756},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.38756},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Polymorph-Tunable Spin Texture and Excitonic Structures in Monolayer WSi2P4
AU - Xianbo Chenwei
AU - Yu Zhou
AU - Ke Wu
AU - Gaofeng Xu
AU - Ruixue Li
AU - Yuan Li
AU - Yabei Wu
AU - Shaowen Xu
AU - Fanhao Jia
PY - 2026
DA - 2026/09/30
PB - arXiv
DO - 10.48550/arxiv.2609.38756
UR - https://arxiv.org/abs/2609.38756
AB - Two-dimensional semiconductors that simultaneously possess a direct band gap and strong spin-orbit coupling (SOC) are highly attractive for quantum optoelectronics. Using first-principles GW plus Bethe-Salpeter equation (GW-BSE) calculations, we show that monolayer WSi2P4-an experimentally accessible member of the MSi2X4 family-hosts a direct K-valley gap together with strong SOC. Its three competing polymorphs (alpha, beta and gamma) are all direct-gap semiconductors and are kinetically locked behind 1.3 eV migration barriers. The sigma_h mirror plane of the D3h of alpha and gamma phases enforces a persistent spin texture across the Brillouin zone, weakly modulated near gamma by interband SOC mixing, whereas the polar beta phase (C3v) exhibits Rashba spin splitting. SOC splits the doubly-degenerate lowest bright exciton into dark states and splits the original absorption peak into two peaks (A and B), whose relative brightness is governed by the K-valley conduction-band splitting. alpha-WSi2P4 displays the brightest Peak A because a tiny band crossing of opposite-spin branches can open a spin-allowed radiative channel. These results establish the MSi2P4 family as a phase-tunable platform for the cooperative engineering of spin texture, band splitting, and excitonic brightness within a single material system.
ER -