Nontrivial topology in ultrathin bismuth nanowires: An electronic transport study.

In the past, bismuth was considered to be topologically trivial on the basis of theoretical study of band inversions and angle resolved photoemission spectroscopy. However, the topological properties of bismuth are the subject of renewed study because of the observations of high mobility exhibited by Bi nanowires (suggesting topological protection) as well as the proposal of higher-order topology. We studied the magnetoresistance (MR) in samples of ultrathin nanowires of bismuth, diameter ~50 nm, that exhibit high mobility (Huber et al, Scientific Reports 7,15569 (2017)). The MR exhibits peaks for a sequence of orientations of the magnetic field B, including a coherence peak for B//(111), that can be interpreted in terms of Yamaji magic angles . Magic angles are observed in layered conductors with an open, corrugated, Fermi surface. In contrast, bulk bismuth does not display magic angles since the Fermi surface consist of small ellipsoids and is closed. We will discuss our interpretation of the observations in terms of inter-Bi bilayer coupling and hinge states.