arXiv subjects

Dirk Reuter

Publications and source records attributed to Dirk Reuter.

42 records · Page 3Linked to original sources

arXiv2007

Strong spin-orbit interactions and weak antilocalization in carbon doped p-type GaAs heterostructures

We present a comprehensive study of the low-field magnetoresistance in carbon doped p-type GaAs/AlGaAs heterostructures aiming at the investigation of spin-orbit interaction effects. The following signatures of exceptionally strong spin-orbit interactions are simultaneously observed: a beating in the Shubnikov-de Haas oscillations, a classical positive magnetoresistance due to the presence of the two spin-split subbands, and a weak anti-localization dip in the magnetoresistance. The spin-orbit induced splitting of the heavy hole subband at the Fermi level is determined to be around 30% of the total Fermi energy. The phase coherence length of holes of around 2.5 $μ$m at a temperature of 70 mK, extracted from weak anti-localization measurements, is promissing for the fabrication of phase-coherent p-type nanodevices.

cond-mat.mes-hall↗

arXiv2007

Aharonov-Bohm oscillations in p-type GaAs quantum rings

We have explored phase coherent transport of holes in two p-type GaAs quantum rings with orbital radii 420 nm and 160 nm fabricated with AFM oxidation lithography. Highly visible Aharonov-Bohm (AB) oscillations are measured in both rings, with an amplitude of the oscillations exceeding 10% of the total resistance in the case of the ring with a radius of 160 nm. Beside the h/e oscillations, we resolve the contributions from higher harmonics of the AB oscillations. The observation of a local resistance minimum at B=0 T in both rings is a signature of the destructive interference of the holes' spins. We show that this minimum is related to the minimum in the h/2e oscillations.

cond-mat.mes-hall↗

arXiv2007

Aharonov-Bohm oscillations in the presence of strong spin-orbit interactions

We have measured highly visible Aharonov-Bohm (AB) oscillations in a ring structure defined by local anodic oxidation on a p-type GaAs heterostructure with strong spin-orbit interactions. Clear beating patterns observed in the raw data can be interpreted in terms of a spin geometric phase. Besides h/e oscillations, we resolve the contributions from the second harmonic of AB oscillations and also find a beating in these h/2e oscillations. A resistance minimum at B=0T, present in all gate configurations, is the signature of destructive interference of the spins propagating along time-reversed paths.

cond-mat.mes-hall↗

arXiv2006

Magneto-optical probing of weak disorder in a two-dimensional hole gas

In two-beam magneto-photoluminescence spectra of a two-dimensional valence hole gas we identify the three-level energy spectrum of a free positive trion with a field-induced singlet-triplet transition. The recombination spectrum of acceptor-bound trions is also detected, including a cyclotron replica corresponding to the hole shake-up process. The emergence of a shake-up peak at low temperature is shown to be a sensitive probe of the presence of a small number of impurities inside the high-mobility quantum well, and its relative position is directly related to the hole cyclotron mass.

cond-mat.mes-hall↗

arXiv2005

Single-hole transistor in p-type GaAs/AlGaAs heterostructures

A single-hole transistor is patterned in a p-type, C-doped GaAs/AlGaAs heterostructure by AFM oxidation lithography. Clear Coulomb blockade resonances have been observed at T=300 mK. A charging energy of ~ 1.5 meV is extracted from Coulomb diamond measurements, in agreement with the lithographic dimensions of the dot. The absence of excited states in Coulomb diamond measurements, as well as the temperature dependence of Coulomb peak heights indicate that the dot is in the multi-level transport regime. Fluctuations in peak spacings larger than the estimated mean single-particle level spacing are observed.

cond-mat.mes-hall↗

arXiv2004

Magneto-capacitance probing of the many-particle states in InAs dots

We use frequency-dependent capacitance-voltage spectroscopy to measure the tunneling probability into self-assembled InAs quantum dots. Using an in-plane magnetic field of variable strength and orientation, we are able to obtain information on the quasi-particle wave functions in momentum space for 1 to 6 electrons per dot. For the lowest two energy states, we find a good agreement with Gaussian functions for a harmonic potential. The high energy orbitals exhibit signatures of anisotropic confinement and correlation effects.

cond-mat.other↗