Coexisting Rashba/Dresselhaus Spin Splitting in Solution-Processed Bournonite Films Using Circular Photogalvanic Effect

Spin-split electronic states, such as the Rashba and Dresselhaus effects, are central to the development of energy-efficient spintronic applications, enabling the manipulation of spin information without applying magnetic fields. While validating spin-split electronic states typically requires sophisticated angle-resolved photoemission spectroscopy under stringent sample preparation conditions, the circular photogalvanic effect (CPGE)— which measures helicity-dependent photocurrent at zero bias—offers a sensitive, nondestructive, and accessible benchtop technique for probing such spin-splitting in solids. Bournonite (CuPbSbS3) is a non-centrosymmetric semiconductor that offers several advantages including Earth-abundant constituents, thermodynamic stability, and compatibility with solution-based thin-film fabrication techniques. Bournonite has been theoretically predicted to host robust spin-split states due to its intrinsic broken bulk inversion symmetry, yet no experimental confirmation has been reported to date. Here, both transverse and longitudinal CPGE responses are measured in solution-processed thin films of bournonite, providing direct support for coexisting Rashba and Dresselhaus spin-split states in this material due to structural and bulk inversion asymmetry, as corroborated with first-principles calculations. The results not only contribute to understanding this material's spintronic potential and its tunable, energy-resolved spin structure, but also demonstrate the utilization of CPGE to identify spin-orbit-driven phenomena across a wide variety of non-centrosymmetric semiconductors.

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Author David Mitzi Thomas Lord Department of Mechanical Engineering and Materia ...