title: Magnetic field-induced helical mode and topological transitions in a topological insulator nanoribbon.
abstract: The spin-helical Dirac fermion topological surface states in a topological insulator nanowire or nanoribbon promise novel topological devices and exotic physics such as Majorana fermions. Here, we report local and non-local transport measurements in Bi2Te3 topological insulator nanoribbons that exhibit quasi-ballistic transport over ∼2 μm. The conductance versus axial magnetic flux Φ exhibits Aharonov-Bohm oscillations with maxima occurring alternately at half-integer or integer flux quanta (Φ0 = h/e, where h is Planck's constant and e is the electron charge) depending periodically on the gate-tuned Fermi wavevector (kF) with period 2π/C (where C is the nanoribbon circumference). The conductance versus gate voltage also exhibits kF-periodic oscillations, anti-correlated between Φ = 0 and Φ0/2. These oscillations enable us to probe the Bi2Te3 band structure, and are consistent with the circumferentially quantized topological surface states forming a series of one-dimensional subbands, which undergo periodic magnetic field-induced topological transitions with the disappearance/appearance of the gapless Dirac point with a one-dimensional spin helical mode.
authors.affiliation: Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA.|School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Jauregui
authors.affiliation: Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Pettes
authors.affiliation: Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA.|School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA.|Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Leonid P
authors.initials: LP
authors.lastname: Rokhinson
authors.affiliation: Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas 78712, USA.|Materials Science and Engineering Program, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Li
authors.identifier: http://orcid.org/0000-0002-5401-6839
authors.initials: L
authors.lastname: Shi
authors.affiliation: Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA.|School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA.|Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Yong P
authors.initials: YP
authors.lastname: Chen