title: Magnetoluminescence and valley polarized state of a two-dimensional electron gas in WS2 monolayers.
abstract: Materials often exhibit fundamentally new phenomena in reduced dimensions that potentially lead to novel applications. This is true for single-layer, two-dimensional semiconductor crystals of transition-metal dichalcogenides, MX2 (M = Mo, W and X = S, Se). They exhibit direct bandgaps with energies in the visible region at the two non-equivalent valleys in the Brillouin zone. This makes them suitable for optoelectronic applications that range from light-emitting diodes to light harvesting and light sensors, and to valleytronics. Here, we report the results of a magnetoluminescence study of WS2 single-layer crystals in which the strong spin-orbit interaction additionally locks the valley and spin degrees of freedom. The recombination of the negatively charged exciton in the presence of a two-dimensional electron gas (2DEG) is found to be circularly polarized at zero magnetic field despite being excited with unpolarized light, which indicates that the existence of a valley polarized 2DEG is caused by valley and spin locking and strong electron-electron interactions.
authors.affiliation: University at Buffalo, SUNY, Buffalo, New York 14260, USA.
authors.forename: T
authors.initials: T
authors.lastname: Scrace
authors.affiliation: University at Buffalo, SUNY, Buffalo, New York 14260, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Tsai
authors.affiliation: University at Buffalo, SUNY, Buffalo, New York 14260, USA.
authors.forename: B
authors.initials: B
authors.lastname: Barman
authors.affiliation: University at Buffalo, SUNY, Buffalo, New York 14260, USA.
authors.forename: L
authors.initials: L
authors.lastname: Schweidenback
authors.affiliation: University at Buffalo, SUNY, Buffalo, New York 14260, USA.
authors.forename: A
authors.initials: A
authors.lastname: Petrou
authors.affiliation: University of Crete, Heraklion GR-71003, Greece.
authors.forename: G
authors.initials: G
authors.lastname: Kioseoglou
authors.affiliation: 1] Quantum Theory Group, Emerging Technologies Division, National Research Council, Ottawa K1A 0R6, Ontario, Canada [2] Department of Physics, University of Ottawa, Ottawa K1N 6N5, Ontario, Canada.
authors.forename: I
authors.initials: I
authors.lastname: Ozfidan
authors.affiliation: Quantum Theory Group, Emerging Technologies Division, National Research Council, Ottawa K1A 0R6, Ontario, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Korkusinski
authors.affiliation: 1] Quantum Theory Group, Emerging Technologies Division, National Research Council, Ottawa K1A 0R6, Ontario, Canada [2] Department of Physics, University of Ottawa, Ottawa K1N 6N5, Ontario, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Hawrylak