Bismuth is a semimetal with a long history in condensed matter that continues
to surprise us today. We demonstrated experimentally that
single crystal Bismuth nanowires carry current predominantly along its
edges in a ballistic way, using superconducting proximity effect.
A recent theoretical work confirmed our findings, by showing that Bismuth belongs to the
newly discovered second order topological class, which means that it carries
one dimensional states living on the hinges of some facets of the three
dimensional crystal. These hinge modes have the exceptional property of having their
their momentum locked to their spin, thereby impeding retro-diffusion in absence of time
reversal symmetry breaking.
Besides ballistic transport, this also implies that the spectrum of the states carrying the
super-current has the peculiarity to have no anticrossing. We could perform a
microwave absorption measurement that demonstrates this property on a well characterized system, up to a frequency
resolution of 0.4 GHz.
|Choix de session parallèle||3.3 Propriétés remarquables des matériaux topologiques : de la théorie à la réalisation expérimentale|