Extremely high excitonic $g$-factors in 2D crystals by alloy-induced admixing of band states
Katarzyna Olkowska-Pucko, Tomasz Woźniak, Elena Blundo, Natalia Zawadzka, Łucja Kipczak, Paulo E. Faria Junior, Jan Szpakowski, Grzegorz Krasucki, Salvatore Cianci, Diana Vaclavkova, Dipankar Jana, Piotr Kapuściński, Amit Pawbake, Shalini Badola, Magdalena Grzeszczyk, Daniele Cecchetti, Giorgio Pettinari, Igor Antoniazzi, Zdeněk Sofer, Iva Plutnarová, Kenji Watanabe, Takashi Taniguchi, Clement Faugeras, Marek Potemski, Adam Babiński, Antonio Polimeni, Maciej R. Molas
Published: 2025/3/29
Abstract
Monolayers (MLs) of semiconducting transition metal dichalcogenides (\mbox{S-TMDs}) emit light very efficiently and display rich spin-valley physics, with gyromagnetic ($g$-) factors of about -4. Here, we investigate how these properties can be tailored by alloying. Magneto-optical spectroscopy is used to reveal the peculiar properties of excitonic complexes in Mo$_{x}$W$_{1-x}$Se$_2$ MLs with different Mo and W concentrations. We show that the alloys feature extremely high $g$-factors for neutral excitons, that change gradually with the composition up to reaching values of the order of -10 for $x \approx 0.2$. First-principles calculations corroborate the experimental findings and provide evidence that alloying in S-TMDs results in a non-trivial band structure engineering, being at the origin of the high $g$-factors. The theoretical framework also suggests a higher strain sensitivity of the alloys, making them promising candidates for tailor-made optoelectronic devices.