  We present low-temperature transport experiments on Aharonov-Bohm (AB) rings
fabricated from two-dimensional hole gases in p-type GaAs/AlGaAs
heterostructures. Highly visible h/e (up to 15%) and h/2e oscillations, present
for different gate voltages, prove the high quality of the fabricated devices.
Like in previous work, a clear beating pattern of the h/e and h/2e oscillations
is present in the magnetoresistance, producing split peaks in the Fourier
spectrum. The magnetoresistance evolution is presented and discussed as a
function of temperature and gate voltage. It is found that sample specific
properties have a pronounced influence on the observed behavior. For example,
the interference of different transverse modes or the interplay between h/e
oscillations and conductance fluctuations can produce the features mentioned
above. In previous work they have occasionally been interpreted as signatures
of spin-orbit interaction (SOI)-induced effects. In the light of these results,
the unambiguous identification of SOI-induced phase effects in AB rings remains
still an open and challenging experimental task.
