Szymon Hennel

Characterization of spin-orbit interactions of GaAs heavy holes using a quantum point contact.

We present transport experiments performed in high-quality quantum point contacts embedded in a GaAs two-dimensional hole gas. The strong spin-orbit interaction results in peculiar transport phenomena, including the previously observed anisotropic Zeeman splitting and level-dependent effective g factors. Here we find additional effects, namely, the crossing and the anticrossing of spin-split levels depending on subband index and magnetic field direction. Our experimental observations are reconciled in a heavy-hole effective spin-orbit Hamiltonian where cubic- and quadratic-in-momentum terms appear. The spin-orbit components, being of great importance for quantum computing applications, are characterized in terms of magnitude and spin structure. In light of our results, we explain the level-dependent effective g factor in an in-plane field. Through a tilted magnetic field analysis, we show that the quantum point contact out-of-plane g factor saturates around the predicted 7.2 bulk value.

Tunnel barrier design in donor nanostructures defined by hydrogen-resist lithography

A four-terminal donor quantum dot (QD) is used to characterize potential barriers between degenerately doped nanoscale contacts. The QD is fabricated by hydrogen-resist lithography on Si(001) in combination with

Stable branched electron flow

n

Nonlocal Polarization Feedback in a Fractional Quantum Hall Ferromagnet.

-type doping by phosphine. The four contacts have different separations (

Aharonov-Bohm rings with strong spin-orbit interaction: the role of sample-specific properties

d

From charge detection to Coulomb drag in hybrid graphene/GaAs devices

= 9, 12, 16 and 29 nm) to the central 6 nm

Investigating energy scales of fractional quantum Hall states using scanning gate microscopy

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Generation and Detection of Spin Currents in Semiconductor Nanostructures with Strong Spin-Orbit Interaction

6 nm QD island, leading to different tunnel and capacitive coupling. Cryogenic transport measurements in the Coulomb-blockade (CB) regime are used to characterize these tunnel barriers. We find that field enhancement near the apex of narrow dopant leads is an important effect that influences both barrier breakdown and the magnitude of the tunnel current in the CB transport regime. From CB-spectroscopy measurements, we extract the mutual capacitances between the QD and the four contacts, which scale inversely with the contact separation

Anomalous Coulomb drag between bilayer graphene and a GaAs electron gas

d

Scanning Gate Microscopy in a Viscous Electron Fluid.

. The capacitances are in excellent agreement with numerical values calculated from the pattern geometry in the hydrogen resist. We show that by engineering the source-drain tunnel barriers to be asymmetric, we obtain a much simpler excited-state spectrum of the QD, which can be directly linked to the orbital single-particle spectrum.