title: Optical Investigation of Monolayer and Bulk Tungsten Diselenide (WSe₂) in High Magnetic Fields.
abstract: Optical spectroscopy in high magnetic fields B ≤ 65 T is used to reveal the very different nature of carriers in monolayer and bulk transition metal dichalcogenides. In monolayer WSe2, the exciton emission shifts linearly with the magnetic field and exhibits a splitting that originates from the magnetic field induced valley splitting. The monolayer data can be described using a single particle picture with a Dirac-like Hamiltonian for massive Dirac Fermions, with an additional term to phenomenologically include the valley splitting. In contrast, in bulk WSe2 where the inversion symmetry is restored, transmission measurements show a distinctly excitonic behavior with absorption to the 1s and 2s states. Magnetic field induces a spin splitting together with a small diamagnetic shift and cyclotron like behavior at high fields, which is best described within the hydrogen model.
authors.affiliation: †Laboratoire National des Champs Magnétiques Intenses, CNRS-EMFL-UJF-UPS-INSA, Grenoble and Toulouse, France.|∥Institute of Applied Physics, Academiei Str. 5, Chisinau, MD-2028, Republic of Moldova.
authors.forename: A A
authors.initials: AA
authors.lastname: Mitioglu
authors.affiliation: †Laboratoire National des Champs Magnétiques Intenses, CNRS-EMFL-UJF-UPS-INSA, Grenoble and Toulouse, France.
authors.forename: P
authors.initials: P
authors.lastname: Plochocka
authors.affiliation: ‡High Field Magnet Laboratory (HFML-EMFL), Institute for Molecules and Materials, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
authors.forename: Á
authors.initials: Á
authors.lastname: Granados del Aguila
authors.affiliation: ‡High Field Magnet Laboratory (HFML-EMFL), Institute for Molecules and Materials, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
authors.forename: P C M
authors.initials: PC
authors.lastname: Christianen
authors.affiliation: §Microelectronics Research Group, FORTH-IESL, 71110 Heraklion, Crete Greece.
authors.forename: G
authors.initials: G
authors.lastname: Deligeorgis
authors.affiliation: ∥Institute of Applied Physics, Academiei Str. 5, Chisinau, MD-2028, Republic of Moldova.
authors.forename: S
authors.initials: S
authors.lastname: Anghel
authors.affiliation: ∥Institute of Applied Physics, Academiei Str. 5, Chisinau, MD-2028, Republic of Moldova.
authors.forename: L
authors.initials: L
authors.lastname: Kulyuk
authors.affiliation: †Laboratoire National des Champs Magnétiques Intenses, CNRS-EMFL-UJF-UPS-INSA, Grenoble and Toulouse, France.
authors.forename: D K
authors.initials: DK
authors.lastname: Maude
keywords: Fermi velocity; Transition metal dichalcogenides; WSe2; bulk; massive Dirac Fermions; monolayer; valley splitting