Electronic and Excitonic Properties of MSi 2 Z 4 Monolayers

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2023-05, Vol.19 (19), p.e2206444
• Main Authors: Woźniak, Tomasz, Umm-E-Hani, Faria Junior, Paulo E, Ramzan, Muhammad S, Kuc, Agnieszka B
• Format: Article
• Language: English
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202206444

MA Z monolayers form a new class of hexagonal non-centrosymmetric materials hosting extraordinary spin-valley physics. While only two compounds (MoSi N and WSi N ) are recently synthesized, theory predicts interesting (opto)electronic properties of a whole new family of such two-dimensional (2D) materials. Here, the chemical trends of band gaps and spin-orbit splittings of bands in selected MSi Z (M = Mo, W; Z = N, P, As, Sb) compounds are studied from first-principles. Effective Bethe-Salpeter-equation-based calculations reveal high exciton binding energies. Evolution of excitonic energies under external magnetic field is predicted by providing their effective g-factors and diamagnetic coefficients, which can be directly compared to experimental values. In particular, large positive g-factors are predicted for excitons involving higher conduction bands. In view of these predictions, MSi Z monolayers yield a new platform to study excitons and are attractive for optoelectronic devices, also in the form of heterostructures. In addition, a spin-orbit induced bands inversion is observed in the heaviest studied compound, WSi Sb , a hallmark of its topological nature.