Magneto-transport in (shaped) topological insulator nanowires
DIPC Seminars
- Speaker
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Cosimo Gorini, Universität Regensburg
- When
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2018/09/11
14:00 - Place
- Donostia International Physics Center
- Add to calendar
-
iCal
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 5 μm 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.
We also discuss the magneto-conductance through shaped (tapered, curved)
nanowires. The nanowire non-constant radius implies a competition between
effects due to quantum confinement and to a spatially varying enclosed
magnetic flux, and offers the possibility of studying quantum Hall physics in
curved space.
Host: Dario Bercioux