TY - JOUR

T1 - Probing spin helical surface states in topological HgTe nanowires

AU - Ziegler, J.

AU - Kozlovsky, R.

AU - Gorini, C.

AU - Liu, M. H.

AU - Weishäupl, S.

AU - Maier, H.

AU - Fischer, R.

AU - Kozlov, D. A.

AU - Kvon, Z. D.

AU - Mikhailov, N.

AU - Dvoretsky, S. A.

AU - Richter, K.

AU - Weiss, D.

PY - 2018/1/29

Y1 - 2018/1/29

N2 - Nanowires with helical surface states represent key prerequisites for observing and exploiting phase-coherent topological conductance phenomena, such as spin-momentum locked quantum transport or topological superconductivity. We demonstrate in a joint experimental and theoretical study that gated nanowires fabricated from high-mobility strained HgTe, known as a bulk topological insulator, indeed preserve the topological nature of the surface states, that moreover extend phase-coherently across the entire wire geometry. The phase-coherence lengths are enhanced up to 5μm when tuning the wires into the bulk gap, so as to single out topological transport. The nanowires exhibit distinct conductance oscillations, both as a function of the flux due to an axial magnetic field and of a gate voltage. The observed h/e-periodic Aharonov-Bohm-type modulations indicate surface-mediated quasiballistic transport. Furthermore, an in-depth analysis of the scaling of the observed gate-dependent conductance oscillations reveals the topological nature of these surface states. To this end we combined numerical tight-binding calculations of the quantum magnetoconductance with simulations of the electrostatics, accounting for the gate-induced inhomogeneous charge carrier densities around the wires. We find that helical transport prevails even for strongly inhomogeneous gating and is governed by flux-sensitive high-angular momentum surface states that extend around the entire wire circumference.

AB - Nanowires with helical surface states represent key prerequisites for observing and exploiting phase-coherent topological conductance phenomena, such as spin-momentum locked quantum transport or topological superconductivity. We demonstrate in a joint experimental and theoretical study that gated nanowires fabricated from high-mobility strained HgTe, known as a bulk topological insulator, indeed preserve the topological nature of the surface states, that moreover extend phase-coherently across the entire wire geometry. The phase-coherence lengths are enhanced up to 5μm when tuning the wires into the bulk gap, so as to single out topological transport. The nanowires exhibit distinct conductance oscillations, both as a function of the flux due to an axial magnetic field and of a gate voltage. The observed h/e-periodic Aharonov-Bohm-type modulations indicate surface-mediated quasiballistic transport. Furthermore, an in-depth analysis of the scaling of the observed gate-dependent conductance oscillations reveals the topological nature of these surface states. To this end we combined numerical tight-binding calculations of the quantum magnetoconductance with simulations of the electrostatics, accounting for the gate-induced inhomogeneous charge carrier densities around the wires. We find that helical transport prevails even for strongly inhomogeneous gating and is governed by flux-sensitive high-angular momentum surface states that extend around the entire wire circumference.

KW - INSULATOR NANORIBBONS

KW - TRANSPORT

KW - CONDUCTORS

UR - http://www.scopus.com/inward/record.url?scp=85041195228&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.97.035157

DO - 10.1103/PhysRevB.97.035157

M3 - Article

AN - SCOPUS:85041195228

VL - 97

JO - Physical Review B

JF - Physical Review B

SN - 2469-9950

IS - 3

M1 - 035157

ER -