title: Ballistic miniband conduction in a graphene superlattice.
abstract: Rational design of long-period artificial lattices yields effects unavailable in simple solids. The moiré pattern in highly aligned graphene/hexagonal boron nitride (h-BN) heterostructures is a lateral superlattice with high electron mobility and an unusual electronic dispersion whose miniband edges and saddle points can be reached by electrostatic gating. We investigated the dynamics of electrons in moiré minibands by measuring ballistic transport between adjacent local contacts in a magnetic field, known as the transverse electron focusing effect. At low temperatures, we observed caustics of skipping orbits extending over hundreds of superlattice periods, reversals of the cyclotron revolution for successive minibands, and breakdown of cyclotron motion near van Hove singularities. At high temperatures, electron-electron collisions suppress focusing. Probing such miniband conduction properties is a necessity for engineering novel transport behaviors in superlattice devices.
authors.affiliation: Department of Physics and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305, USA.
authors.forename: Menyoung
authors.initials: M
authors.lastname: Lee
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.
authors.forename: John R
authors.initials: JR
authors.lastname: Wallbank
authors.affiliation: Department of Physics and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Gallagher
authors.affiliation: National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK. School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Vladimir I
authors.initials: VI
authors.lastname: Fal'ko
authors.affiliation: Department of Physics and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305, USA. goldhaber-gordon@stanford.edu.
authors.forename: David
authors.initials: D
authors.lastname: Goldhaber-Gordon