Unidirectional Rashba Spin Splitting in Single Layer WS\(_{2(1-x)}\)Se\(_{2x}\) alloy

• Published in: arXiv.org 2022-12
• Main Authors: Zribi, Jihene, Pierucci, Debora, Bisti, Federico, Zheng, Biyuan, Avila, Josse, Khalil, Lama, Ernandes, Cyrine, Chaste, Julien, Oehler, Fabrice, Pala, Marco, Maroutian, Thomas, Hermes, Ilka, Lhuillier, Emmanuel, Pan, Anlian, Ouerghi, Abdelkarim
• Format: Article
• Language: English
• Subjects: Alloys; Anisotropy; Crystal structure; Electric dipoles; Electronegativity; Electronic properties; Electronic structure; Linear polarization; Microscopy; Parabolic bodies; Photoelectric emission; Photoelectron spectroscopy; Photoluminescence; Piezoelectricity; Spectrum analysis; Spintronics; Splitting; Tensile strain; Transition metal compounds; Two dimensional materials; Valence band
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2212.03248

Atomically thin two-dimensional (2D) layered semiconductors such as transition metal dichalcogenides (TMDs) have attracted considerable attention due to their tunable band gap, intriguing spin-valley physics, piezoelectric effects and potential device applications. Here we study the electronic properties of a single layer WS\(_{1.4}\)Se\(_{0.6}\) alloys. The electronic structure of this alloy, explored using angle resolved photoemission spectroscopy, shows a clear valence band structure anisotropy characterized by two paraboloids shifted in one direction of the k-space by a constant in-plane vector. This band splitting is a signature of a unidirectional Rashba spin splitting with a related giant Rashba parameter of 2.8 0.7 eV . The combination of angle resolved photoemission spectroscopy with piezo force microscopy highlights the link between this giant unidirectional Rashba spin splitting and an in-plane polarization present in the alloy. These peculiar anisotropic properties of the WS\(_{1.4}\)Se\(_{0.6}\) alloy can be related to local atomic orders induced during the growth process due the different size and electronegativity between S and Se atoms. This distorted crystal structure combined to the observed macroscopic tensile strain, as evidenced by photoluminescence, displays electric dipoles with a strong in-plane component, as shown by piezoelectric microscopy. The interplay between semiconducting properties, in-plane spontaneous polarization and giant out-of-plane Rashba spin-splitting in this two-dimensional material has potential for a wide range of applications in next-generation electronics, piezotronics and spintronics devices.