Alloy engineering of excitonic properties in TMD monolayers

2026/08/04 by Eirini Katsipoulaki, Adlen Smiri, Panagiotis Spiliotakis +12
Physics and Astronomy · #cond-mat.mtrl-sci

paper · pdf

11 pages, 4 figures

arxiv created 2026/08/04 · arxiv updated 2026/08/05

Abstract

We investigate monolayer MoS_2xSe_2(1-x) alloys across the full composition range using optical spectroscopy. We demonstrate continuous tuning of the optical gap over ∼0.35 eV, accompanied by a systematic reduction of the B--A exciton splitting, in agreement with density functional theory calculations. Temperature-dependent measurements reveal a progressive increase of the average phonon energy from Se-rich to S-rich alloys that follows a simple reduced-mass scaling model. Polarization-resolved spectroscopy further shows a monotonic increase of the circular polarization from nearly zero in MoSe₂ to ∼15% in MoS₂ at 78 K. The observed evolution of the polarization is attributed to alloy-induced modifications of the electronic structure that modify bright--dark exciton mixing and the associated valley depolarization. These findings establish alloy engineering as an effective strategy for controlling excitonic properties in TMD monolayers.

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