Year: 2026
Type: preprint
Abstract: Magnetic fields are widely used to brighten spin-forbidden dark excitons, but the inverse effect on an optically bright exciton has remained largely unexplored. We demonstrate the complementary phenomenon of magnetic-field-induced darkening of a bright exciton in Mo$_{0.68}$W$_{0.32}$Se$_2$. At 4.2 K, an in-plane magnetic field up to 25 T activates a dark-exciton line 14.2$\pm$1.3 meV below the bright exciton while suppressing the bright-exciton emission by about 85\%. A bright-dark mixing model quantitatively captures the coupled energy and intensity evolution with an effective in-plane $g$ factor of $|g_{\parallel}|=5.2\pm0.2$. Alloying is crucial to the effect, as it brings the system close to the bright-dark crossover, where a small bright-dark splitting is combined with unusually strong in-plane magnetic coupling. This places the system in a regime where field-induced level repulsion raises the bright-like branch and strongly depletes its thermal population. These results identify a general route to magnetic control of exciton populations through engineering of the bright-dark hierarchy.
Source: arXiv (Cornell University)
Authors: Olkowska-Pucko, Katarzyna, Slobodeniuk, Artur O., Arfaoui, Mehdi, Blundo, Elena, Zawadzka, Natalia, Kipczak, Łucja, Szpakowski, Jan, Vaclavkova, Diana, Jana, Dipankar, Kapuściński, Piotr, Watanabe, Kenji, Taniguchi, Takashi, Faugeras, Clement, Potemski, Marek, Babiński, Adam, Polimeni, Antonio, Molas, Maciej R.
Institutions: University of Warsaw, Warsaw University of Technology, Charles University, Centre National de la Recherche Scientifique, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Université Paris-Saclay, Office National d'Études et de Recherches Aérospatiales, Laboratoire d'Étude des Microstructures, Sapienza University of Rome, Laboratoire National des Champs Magnétiques Intenses, Université Grenoble Alpes, National University of Singapore, Institute for Functional Intelligent Materials, National Institute for Materials Science, Research Center for Materials Nanoarchitectonics
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7223084995