title: Electrostatic coupling between two surfaces of a topological insulator nanodevice.
abstract: We report on electronic transport measurements of dual-gated nanodevices of the low-carrier density topological insulator (TI) Bi_{1.5}Sb_{0.5}Te_{1.7}Se_{1.3}. In all devices, the upper and lower surface states are independently tunable to the Dirac point by the top and bottom gate electrodes. In thin devices, electric fields are found to penetrate through the bulk, indicating finite capacitive coupling between the surface states. A charging model allows us to use the penetrating electric field as a measurement of the intersurface capacitance C_{TI} and the surface state energy-density relationship μ(n), which is found to be consistent with independent angle-resolved photoemission spectroscopy measurements. At high magnetic fields, increased field penetration through the surface states is observed, strongly suggestive of the opening of a surface state band gap due to broken time-reversal symmetry.
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Valla
authors.initials: V
authors.lastname: Fatemi
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Hunt
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA and Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel.
authors.forename: Hadar
authors.initials: H
authors.lastname: Steinberg
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Eltinge
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Fahad
authors.initials: F
authors.lastname: Mahmood
authors.affiliation: Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, MS 6100 Gaithersburg, Maryland 20899, USA and Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742, USA and Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Butch
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Nuh
authors.initials: N
authors.lastname: Gedik
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Ashoori
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Pablo
authors.initials: P
authors.lastname: Jarillo-Herrero