Localization and field-periodic conductance fluctuations in trilayer graphene

We have systematically studied quantum transport in a short trilayer-graphene field-effect transistor. Close to the charge neutrality point, our magnetoconductance data are well described by the theory of weak localization in monolayer graphene. However, as the carrier density is increased we find a complex evolution of the low field magnetoconductance that originates from a combination of the monolayer-like and bilayer-like band structures. The increased phase coherence length at high hole densities takes our shortest devices into the mesoscopic regime with the appearance of significant conductance fluctuations on top of the localization effects. Although these are aperiodic in gate voltage, they exhibit a quasi-periodic behaviour as a function of magnetic field. We show that this is consistent with the interference of discrete trajectories in open quantum dots and discuss the possible origin of these in our devices.