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Alloy engineering of excitonic properties in TMD monolayers

Eirini Katsipoulaki1, Adlen Smiri2, Panagiotis Spiliotakis1,3, Konstantinos Mourzidis2, Danae Katrisioti1,3, Takashi Taniguchi4, Kenji Watanabe5, Georgios Kopidakis1,3, Zdeněk Sofer6 et al.

Gang Wang7, Emmanuel Stratakis1, George Kioseoglou1,3, Iann C. Gerber2,*, Xavier Marie2,8,†, and Ioannis Paradisanos1,3,‡

  • *Contact author: igerber@insa-toulouse.fr
  • †Contact author: marie@insa-toulouse.fr
  • ‡Contact author: iparad@iesl.forth.gr
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Phys. Rev. Materials 10, 104010 – Published 26 October, 2026

DOI: https://doi.org/10.1103/m7kc-8q5v

Abstract

Alloy engineering offers a powerful route to tailor the optoelectronic properties of two-dimensional semiconductors. However, a comprehensive understanding of how alloy composition simultaneously affects the electronic structure, excitonic response, vibrational properties, and spin-valley physics remains limited. Here, we investigate monolayer MoS2xSe2(1−x) alloys across the full composition range using optical spectroscopy. We demonstrate continuous tuning of the optical gap over ∼0.35eV, accompanied by a systematic reduction of the A-B 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 transition-metal-dichalcogenide monolayers.

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Phys. Rev. Materials 10, 104010– Published 26 October, 2026
  • Received 7 July 2026
  • Accepted 8 October 2026
Article part of CHORUS
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