Sven S. Buchholz

Nonlocal Aharonov–Bohm conductance oscillations in an asymmetric quantum ring

We investigate ballistic transport and quantum interference in a nanoscale quantum wire loop fabricated as a GaAs/AlGaAs field-effect heterostructure. Four-terminal measurements of current and voltage characteristics as a function of top gate voltages show negative bend resistance as a clear signature of ballistic transport. In perpendicular magnetic fields, phase-coherent transport leads to Aharonov–Bohm conductance oscillations, which show equal amplitudes in the local and the nonlocal measurement at a temperature of 1.5 K and above. We attribute this observation to the symmetry of the orthogonal cross junctions connecting the four quantum wire leads with the asymmetric quantum wire ring.

Control of the transmission phase in an asymmetric four-terminal Aharonov-Bohm interferometer

Phase sensitivity and thermal dephasing in coherent electron transport in quasi-one-dimensional (1D) waveguide rings of an asymmetric four-terminal geometry are studied by magnetotransport measurements. We demonstrate the electrostatic control of the phase in Aharonov-Bohm resistance oscillations and investigate the impact of the measurement circuitry on decoherence. Phase rigidity is broken due to the ring geometry: orthogonal waveguide cross junctions and 1D leads minimize reflections and resonances between leads allowing for a continuous electron transmission phase shift. The measurement circuitry influences dephasing: thermal averaging dominates in the nonlocal measurement configuration while additional influence of potential fluctuations becomes relevant in the local configuration.

Phase shifts and phase π jumps in four-terminal waveguide Aharonov-Bohm interferometers

Quantum coherent properties of electrons can be studied in Aharonov-Bohm (AB) interferometers. We investigate both experimentally and theoretically the transmission phase evolution in a four-terminal quasi-one-dimensional AlGaAs/GaAs-based waveguide AB ring. As main control parameter besides the magnetic field, we tune the Fermi wave number along the pathways using a top-gate. Our experimental results and theoretical calculations demonstrate the strong influence of the measurement configuration upon the AB-resistance-oscillation phase in a four-terminal device. While the nonlocal setup displays continuous phase shifts of the AB oscillations, the phase remains rigid in the local voltage-probe setup. Abrupt phase jumps are found in all measurement configurations. We analyze the phase shifts as functions of the magnetic field and the Fermi energy and provide a detailed theoretical model of the device. Scattering and reflections in the arms of the ring are the source of abrupt phase jumps by

Noise thermometry in narrow two-dimensional electron gas heat baths connected to a quasi-one-dimensional interferometer

\ensuremath{\pi}

Electrical and terahertz magnetospectroscopy studies of laser-patterned micro- and nanostructures on InAs-based heterostructures

.

Mode-selected heat flow through a one-dimensional waveguide network

Thermal voltage noise measurements are performed in order to determine the electron temperature in nanopatterned channels of a GaAs/AlGaAs heterostructure at bath temperatures of 4.2 and 1.4 K. Two narrow two-dimensional (2D) heating channels are connected by a quasi-1D quantum interferometer. Under dc current heating of the electrons in one heating channel, we perform cross-correlated noise measurements locally in the directly heated channel and nonlocally in the other channel, which is indirectly heated by hot electron diffusion across the quasi-1D connection. The temperature dependence of the electron energy-loss rate is reduced compared to wider 2D systems. Under nonlocal current heating, which establishes a thermal gradient across the quantum interferometer, we show the decoherence in this structure by Aharonov-Bohm measurements.

Mode-filtered electron injection into a waveguide interferometer

Nanostructures fabricated from narrow-gap semiconductors with strong spin-orbit interaction (SOI), such as InAs, can be used to filter momentum modes of electrons and offer the possibility to create and detect spin-polarized currents entirely by electric fields. Here, we present magnetotransport and THz magnetospectroscopy investigations of Hall-bars with back-gates made from in InGaAs/InAlAs quantum well structures with a strained 4 nm InAs inserted channel. The two-dimensional electron gas is at 53 nm depth and has a carrier density of about

TRANSPORT PROPERTIES OF TUNNEL-COUPLED ONE-DIMENSIONAL CHANNELS FROM AN ELECTRON BILAYER SYSTEM IN PERPENDICULAR MAGNETIC FIELD

6\times10^{11}

Thermal energy and charge currents in multi-terminal nanorings

cm

Magnetic‐field reentrant wave function hybridization in stacked one‐dimensional electron systems

^{-2}