10 research outputs found
Robust Helical Edge Transport in Quantum Spin Hall Quantum Wells
We show that burying of the Dirac point in semiconductor-based
quantum-spin-Hall systems can generate unexpected robustness of edge states to
magnetic fields. A detailed band-structure analysis reveals
that InAs/GaSb and HgTe/CdTe quantum wells exhibit such buried Dirac points. By
simulating transport in a disordered system described within an effective
model, we further demonstrate that buried Dirac points yield nearly quantized
edge conduction out to large magnetic fields, consistent with recent
experiments.Comment: 11 pages, 6 figure
Giant spin-orbit splitting in inverted InAs/GaSb double quantum wells
Transport measurements in inverted InAs/GaSb quantum wells reveal a giant
spin-orbit splitting of the energy bands close to the hybridization gap. The
splitting results from the interplay of electron-hole mixing and spin-orbit
coupling, and can exceed the hybridization gap. We experimentally investigate
the band splitting as a function of top gate voltage for both electron-like and
hole-like states. Unlike conventional, noninverted two-dimensional electron
gases, the Fermi energy in InAs/GaSb can cross a single spin-resolved band,
resulting in full spin-orbit polarization. In the fully polarized regime we
observe exotic transport phenomena such as quantum Hall plateaus evolving in
steps and a non-trivial Berry phase
Spin-orbit interaction in a dual gated InAs/GaSb quantum well
Spin-orbit interaction is investigated in a dual gated InAs/GaSb quantum
well. Using an electric field the quantum well can be tuned between a single
carrier regime with exclusively electrons as carriers and a two-carriers regime
where electrons and holes coexist. Spin-orbit interaction in both regimes
manifests itself as a beating in the Shubnikov-de Haas oscillations. In the
single carrier regime the linear Dresselhaus strength is characterized by
28.5 meV and the Rashba coefficient is tuned from 75 to
53 meV by changing the electric field. In the two-carriers regime the spin
splitting shows a nonmonotonic behavior with gate voltage, which is consistent
with our band structure calculations
Spin-orbit interaction and induced superconductivity in a one-dimensional hole gas
\u3cp\u3eLow dimensional semiconducting structures with strong spin-orbit interaction (SOI) and induced superconductivity attracted great interest in the search for topological superconductors. Both the strong SOI and hard superconducting gap are directly related to the topological protection of the predicted Majorana bound states. Here we explore the one-dimensional hole gas in germanium silicon (Ge-Si) core-shell nanowires (NWs) as a new material candidate for creating a topological superconductor. Fitting multiple Andreev reflection measurements shows that the NW has two transport channels only, underlining its one-dimensionality. Furthermore, we find anisotropy of the Landé g-factor that, combined with band structure calculations, provides us qualitative evidence for the direct Rashba SOI and a strong orbital effect of the magnetic field. Finally, a hard superconducting gap is found in the tunneling regime and the open regime, where we use the Kondo peak as a new tool to gauge the quality of the superconducting gap.\u3c/p\u3
Spin-orbit interaction and induced superconductivity in a one-dimensional hole gas
Low dimensional semiconducting structures with strong spin-orbit interaction (SOI) and induced superconductivity attracted great interest in the search for topological superconductors. Both the strong SOI and hard superconducting gap are directly related to the topological protection of the predicted Majorana bound states. Here we explore the one-dimensional hole gas in germanium silicon (Ge-Si) core-shell nanowires (NWs) as a new material candidate for creating a topological superconductor. Fitting multiple Andreev reflection measurements shows that the NW has two transport channels only, underlining its one-dimensionality. Furthermore, we find anisotropy of the Landé g-factor that, combined with band structure calculations, provides us qualitative evidence for the direct Rashba SOI and a strong orbital effect of the magnetic field. Finally, a hard superconducting gap is found in the tunneling regime and the open regime, where we use the Kondo peak as a new tool to gauge the quality of the superconducting gap