Topological superconductors are of current research interest, because of their potential applications for building topological quantum computers. They are predicted to host bulk supercurrents and excitations in their edge states, also known as Majorana fermions. However, much less is known about the intrinsic supercurrent that occurs in the edge state. In this seminar, we discuss the first discovery of intrinsic edge supercurrent in a Weyl superconductor MoTe2 and present its use for probing the interaction between incompatible superconducting condensates in a hybrid system.
We present the evidence for an intrinsic edge supercurrent in the superconducting phase of a type-II Weyl semimetal MoTe2. In a nanodevice, made of an exfoliated MoTe2 crystal and trivial gold contacts, values of critical current exhibit periodic modulations with respect to the applied magnetic field. The area, associated with this period, scales with an increasing magnetic field and matches the physical area of device at a larger field. These trends suggest the fluxoid quantization by the one-dimensional edge supercurrent. The Ginzburg-Landau description of edge-induced fluxoid quantization leads to the varying edge superfluid velocity and the characteristic scalloped boundary in critical current.
In a hybrid system that consists of a MoTe2 device and a coupled s-wave superconductor, the edge state of MoTe2 can detect the interaction between two competing superconducting condensates. The incompatibility of intrinsic bulk and s-wave condensate results in the stochastic switching of critical current and anomalous antihysteretic behaviors with the wrong sign. The injected supercurrent on the edge mode leads to fluxoid-induced oscillations of critical current that persist up to a very high magnetic field. The oscillations are either noisy or noise-free, depending on the superconducting condensate that prevails on the edge. The phase noise from edge mode reveals the competition between the two condensates and uncovers the novel blockade mechanism, where the intrinsic bulk condensate blocks the proximitization of s-wave superconductor depending on the history.