title: High electron mobility, quantum Hall effect and anomalous optical response in atomically thin InSe.
abstract: A decade of intense research on two-dimensional (2D) atomic crystals has revealed that their properties can differ greatly from those of the parent compound. These differences are governed by changes in the band structure due to quantum confinement and are most profound if the underlying lattice symmetry changes. Here we report a high-quality 2D electron gas in few-layer InSe encapsulated in hexagonal boron nitride under an inert atmosphere. Carrier mobilities are found to exceed 103cm2V-1s-1and 104cm2V-1s-1at room and liquid-helium temperatures, respectively, allowing the observation of the fully developed quantum Hall effect. The conduction electrons occupy a single 2D subband and have a small effective mass. Photoluminescence spectroscopy reveals that the bandgap increases by more than 0.5 eV with decreasing the thickness from bulk to bilayer InSe. The band-edge optical response vanishes in monolayer InSe, which is attributed to the monolayer's mirror-plane symmetry. Encapsulated 2D InSe expands the family of graphene-like semiconductors and, in terms of quality, is competitive with atomically thin dichalcogenides and black phosphorus.
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors.forename: Denis A
authors.initials: DA
authors.lastname: Bandurin
authors.affiliation: Skolkovo Institute of Science and Technology, Nobel St. 3, 143026 Moscow, Russia.|National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Anastasia V
authors.initials: AV
authors.lastname: Tyurnina
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors.forename: Geliang L
authors.initials: GL
authors.lastname: Yu
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors.forename: Artem
authors.identifier: 0000-0002-0427-5664
authors.initials: A
authors.lastname: Mishchenko
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Viktor
authors.initials: V
authors.lastname: Zólyomi
authors.affiliation: Institute of Microelectronics Technology and High Purity Materials, RAS, Chernogolovka 142432, Russia.|National University of Science and Technology 'MISiS', Leninsky Pr. 4, 119049 Moscow, Russia.
authors.forename: Sergey V
authors.initials: SV
authors.lastname: Morozov
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Roshan Krishna
authors.initials: RK
authors.lastname: Kumar
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Roman V
authors.initials: RV
authors.lastname: Gorbachev
authors.affiliation: School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK.
authors.forename: Zakhar R
authors.initials: ZR
authors.lastname: Kudrynskyi
authors.affiliation: High Field Magnet Laboratory (HFML -EMFL), Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
authors.forename: Sergio
authors.initials: S
authors.lastname: Pezzini
authors.affiliation: National Academy of Sciences of Ukraine, Institute for Problems of Materials Science, UA-58001 Chernovtsy, Ukraine.
authors.forename: Zakhar D
authors.initials: ZD
authors.lastname: Kovalyuk
authors.affiliation: High Field Magnet Laboratory (HFML -EMFL), Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
authors.forename: Uli
authors.initials: U
authors.lastname: Zeitler
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Konstantin S
authors.initials: KS
authors.lastname: Novoselov
authors.affiliation: School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK.
authors.forename: Amalia
authors.initials: A
authors.lastname: Patanè
authors.affiliation: School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK.
authors.forename: Laurence
authors.initials: L
authors.lastname: Eaves
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors.forename: Irina V
authors.identifier: 0000-0001-5991-7778
authors.initials: IV
authors.lastname: Grigorieva
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.|National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Vladimir I
authors.initials: VI
authors.lastname: Fal'ko
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors.forename: Andre K
authors.initials: AK
authors.lastname: Geim
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.|National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Yang
authors.initials: Y
authors.lastname: Cao