Eavesdropping on competing condensates by the edge supercurrent in a Weyl superconductor

TL;DR

This paper investigates how edge supercurrents in a Weyl superconductor reveal the interplay and competition between intrinsic and induced pairing symmetries, using fluxoid oscillations and noise analysis to probe underlying condensate states.

Contribution

It demonstrates that the intrinsic pair condensate in MoTe₂ can be incompatible with externally injected s-wave pairing, leading to observable stochastic and anomalous behaviors in supercurrent properties.

Findings

Edge supercurrents exhibit fluxoid oscillations that persist at high magnetic fields.

Incompatibility between intrinsic and induced pairing causes stochastic switching currents.

Phase noise analysis reveals a blockade mechanism affecting condensate proximity.

Abstract

In a topological insulator the metallic surface states are easily distinguished from the insulating bulk states (FuKane07). By contrast, in a topological superconductor (FuKane08,Qi,FuBerg,Oppen), much less is known about the relationship between an edge supercurrent and the bulk pair condensate. Can we force their pairing symmetries to be incompatible? In the superconducting state of the Weyl semimetal MoTe$_2$, an edge supercurrent is observed as oscillations in the current-voltage (\emph{I-V}) curves induced by fluxoid quantization (Wang). We have found that the $s$-wave pairing potential of supercurrent injected from niobium contacts is incompatible with the intrinsic pair condensate in MoTe$_2$. The incompatibility leads to strong stochasticity in the switching current $I_c$ as well as other anomalous properties such as an unusual antihysteretic behavior of the ``wrong'' sign. Under supercurrent injection, the fluxoid-induced edge oscillations survive to much higher magnetic fields \emph{H}. Interestingly, the oscillations are either very noisy or noise-free depending on the pair potential that ends up dictating the edge pairing. Using the phase noise as a sensitive probe that eavesdrops on the competiting bulk states, we uncover an underlying blockade mechanism whereby the intrinsic condensate can pre-emptively block proximitization by the Nb pair potential depending on the history.