Observation of Quantum Oscillations in Single Crystal Bi Nanowires

Abstract

We present here experimental measurements of Aharonov-Bohm (AB) oscillations on single Bi nanowires with diameter d < 80 nm. The single nanowire samples were prepared by Ulitovsky technique and represented cylindrical single crystals with (1011) orientation along the wire axis. Due to semimetal-to-semiconductor transformation and big density of surface states Bi nanowire (d ~ 50 nm) effectively turn into conducting tube. The oscillations of longitudinal magnetoresistance (MR) of Bi nanowires with two periods ∆B1 and ∆ B2 proportional to Φ0 and Φ0/2 were observed, where Φ0=h/e is the flux quantum. From B ~ 8 T down to B = 0 the extremums of Φ0/2 oscillations are shifted up to 3π at B = 0 which is the manifestation of Berry phase shift due to electron moving in nonuniform magnetic field. Derivative of MR was measured at various inclined angles. The observed angle variation of the periods are not in the agreement with theoretical dependence ∆B(α)= ∆B(0)/cosα of the size effect oscillations of the “flux quantization” type. Moreover the equidistant oscillations of MR exist in transverse magnetic fields under certain rotation angles. An interpretation of the MR oscillations is presented.