title: Magnetotransport in atomic-size bismuth contacts.
abstract: We report low-temperature transport experiments on atomic-size contacts of bismuth that are fabricated using the mechanically controlled break-junction technique at low temperatures. We observe stable contacts with conductance values at fractions of one conductance quantum G0 = 2e(2)/h, as is expected for systems with long Fermi wavelength. We defer two preferred conductance scales: the lower one is in the order of 0.015 G0 and can be attributed to single-atom Bi contact, while the higher one amounts to 0.15 G0, as indicated by the appearance of multiples of this value in the conductance histogram. Rich magneto-transport behaviour with significant changes in the magneto-conductance is found in the whole conductance range. Although for the pristine samples and large contacts with G > 5 G0, indications for Shubnikov-de Haas oscillations are present, the smallest contacts show pronounced conductance fluctuations that decay rapidly when a magnetic field is applied. Moreover, large variations are observed when a finite bias voltage is applied. These findings are interpreted as the transition from the diffusive to the ballistic and the ultra-quantum regime when lowering the contact size.
authors.affiliation: Now at Fraunhofer IPM, Heidenhofstraße 8, 79110 Freiburg.
authors.forename: Hans-Fridtjof
authors.initials: HF
authors.lastname: Pernau
authors.forename: Torsten
authors.initials: T
authors.lastname: Pietsch
authors.forename: Elke
authors.initials: E
authors.lastname: Scheer