Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 20: Topological Semimetals II

TT 20.12: Talk

Monday, March 12, 2018, 18:00–18:15, A 053

Ballistic edge states in Bismuth nanowires revealed by SQUID interferometry — •Anil Murani — Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France — Quantronics Group, Service de Physique de l'État Condensé (CNRS UMR 3680 ), IRAMIS, CEA-Saclay, 91191 Gif-sur-Yvette, France

Topological insulators are materials that have electronic states lying at their edges, which are protected against backscattering by time reversal symmetry. Bismuth, a semi-metal with strong spin-orbit coupling, was predicted to be topological in the case of a bilayer thick crystal. We showed numerically that edge states still exists in Bi nanowires, and experimentally demonstrated the existence of edge conduction channels as well as their ballisticity in a recent work, by embedding the nanowire into an asymetric SQUID. The goal of the present study is to go one step further and to answer quantitatively about the topological protection against backscattering as well as the lifetime of the metastable Andreev bound states that can be formed in these topological SNS junction. This is done by inductively coupling the NS loop to a multimode superconducting resonator, with eigenfrequencies ranging from 300 MHz up to 6 GHz, and measuring the magnetic flux dependent absorbtion at the vicinity of each of these frequencies. The resulting phase dependent absorbtion spectrum is measured for different temperatures and can be analyzed using a simple low energy model taking into account two Andreev bound states that nearly anticross, in agreement with a topological protection.