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

Fabrizio Nichele (1), Yashar. Komijani (1), Theodore Choi (1), Dirk Reuter (2), Andreas Wieck (2), Werner Wegscheider(1), Thomas Ihn (1) and Klaus Ensslin

(1) Solid State Physics Laboratory, ETH Zurich – 8093 Zurich, Switzerland
(2) Angewandte Festkörperphysik, Ruhr-Universität Bochum – 44780 Bochum, Germany

Two-dimensional systems with high spin-orbit interaction (SOI) are of particular interest regarding possible spintronics applications. In this framework, nanodevices implemented in p-type GaAs/AlGaAs heterostructures are promising candidates for the realization of quantum information processing and the study of physical phenomena related to carrier-carrier Coulomb interaction and SOI. Recent theoretical and experimental effort has been spent in the study of transport properties of Aharonov-Bohm (AB) rings embedded in materials with strong spin-orbit interaction (SOI). This system is in fact considered as a possible candidate to experimentally observe spin geometric phases (Berry phase and Aharonov-Casher phase) that are usually difficult to access in a transport experiment.

Here we present the transport properties of tunable AB rings embedded in two-dimensional hole gases in p-type GaAs/AlGaAs heterostructures. Highly visible h/e and h/2e oscillations, present in many gates configurations, prove the high quality of the fabricated devices.
As in previous works, a clear beating pattern of the h/e and h/2e oscillations is observed in the magnetoresistance of the rings, producing peak splittings in the Fourier spectrum. An oscillating complex pattern is obsered when the h/e and h/2e oscillations are measured in function of the electrostatic potential. The magnetoresistance evolution with respect to temperature and gate voltage is presented and discussed, underlining how sample specific properties, for example the interference of different transverse modes or the interplay between h/e oscillations and conductance fluctuations could produce the features cited above and often interpreted as signatures of SOI induced effects.
Our poster discusses how the unambiguous identification of SOI induced phase effects in p-type AB rings is still an open and challenging experimental task."