Observation of three-dimensional behavior in surface states of bismuth nanowires and the evidence for bulk Bi charge fractionalization

TL;DR

This study reveals that surface states in bismuth nanowires exhibit three-dimensional behavior, challenging expectations of two-dimensionality, and provides evidence supporting bulk charge fractionalization phenomena.

Contribution

It demonstrates the three-dimensional nature of surface states in bismuth nanowires and offers an alternative interpretation for charge fractionalization observations.

Findings

Surface states show three-dimensional behavior in nanowires.

Long penetration length leads to a spherical Fermi surface.

Magnetoquantum peaks may originate from surface states, not just 2D electron gas.

Abstract

Whereas bulk bismuth supports very-high mobility, light, Dirac electrons and holes in its interior, its boundaries support a layer of heavy electrons in surface states formed by spin orbit interaction in the presence of the surface electric field. Small diameter d trigonal Bi nanowires (30 nm < d < 200 nm) were studied via magnetotransport at low temperatures and for fields up to 14 T in order to investigate the role of surfaces in electronic transport. A two-dimensional behavior was expected for surface charges; however we found instead a three-dimensional behavior, with a rich spectrum of Landau levels in a nearly spherical Fermi surface. This is associated with the long penetration length of surface states of trigonal wires. The prospect of the participation of surface transport and surface-induced relaxation of bulk carriers in the electronic properties of macroscopic samples is evaluated. We show that recent observations of magnetoquantum peaks in the Nernst thermopower coefficient, attributed to two-dimensional electron gas charge fractionalization, can be more plausibly interpreted in terms of these surface states.