School of Physical and Chemical Sciences Te Kura Matū Seminar Series

Topological Hinge States in Bismuth Nanowire Probed by SQUID Interferometry


Taro Wakamura


Laboratoire de Physique des Solides, Université Paris-Sud and Université Paris-Saclay, Orsay, France

Time & Place

Thu, 15 Nov 2018 11:00:00 NZDT in Room 701, Level 7, West Building

All are welcome


Topological insulators (TI) are a new class of materials that exhibit striking quantum effects that are characterized by a bulk band gap and conductive edges or surface states. There have been a large number of theoretical and experimental studies in the search for new TIs both in two-dimensions (2D) and in three-dimensions (3D).

Bismuth (Bi) is a candidate for 2D TIs in the form of bilayer on the (111) surface [1]. Recently, it has also been predicted to be a “Higher-order topological insulator”, whereby the current is carried by two counter-propagating ballistic edge states (without any dissipation), and with the spin orientation locked to that of the propagation direction giving rise to a helical edge state. Thus, the topology is protected by the crystalline symmetry and accompanied by the ballistic helical hinge states [2].

In this study, we demonstrate the existence of ballistic helical hinge channels on a Bi nanowire by fabricating a Josephson junction (JJ) with tungsten superconducting contacts deposited by focused ion beam (FIB). Fraunhofer patterns of the junction show supercurrents distributed locally at the hinges in the Bi nanowire. Employing SQUID interferometry, we observe the saw-tooth shape of the current-phase relation of the Bi-JJ, which is a signature of the ballistic nature of topological hinge channels [3].

[1] S. Murakami, Phys. Rev. Lett. 97, 236805 (2006).

[2] F. Schindler et al., Nat. Phys. 14, 928 (2018).

[3] A. Murani et al., Nat. Commun. 8, 15941 (2017).

All Welcome