Electronic and Excitonic Properties of MSi2Z4 Monolayers

Tomasz Wozniak, Paulo E. Umm-e-hani, Paulo Faria S. Junior,Muhammad B. Ramzan,Agnieszka Kuc

SMALL（2023）

Wroclaw Univ Sci & Technol | Jacobs Univ Bremen | Univ Regensburg

Cited 17|Views45

Abstract

MA(2)Z(4) monolayers form a new class of hexagonal non-centrosymmetric materials hosting extraordinary spin-valley physics. While only two compounds (MoSi2N4 and WSi2N4) 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(2)Z(4) (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(2)Z(4) 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, WSi2Sb4, a hallmark of its topological nature.

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Key words

2D MA(2)Z(4) materials,density functional theory,excitons,g-factors,model Bethe-Salpeter equation

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