Fig. 3: Reversible transitions between YSR states and a robust ZBP/MZM induced by modulating the exchange coupling of type-II Fe adatoms using the STM tip.
a Schematics illustrating an approaching STM tip on top of a type-II Fe adatom can move the Fe adatom in directions parallel and perpendicular to the Te/Se surface and modulate the spin–orbit exchange coupling (Jex) to the superconductor. b Schematic phase diagram from the vortex-free YSR states to an anomalous vortex MZM represented by the ZBP with the increasing exchange coupling Jex. c and d Tunnel-barrier conductance dependence of the dI/dV spectra in c and its intensity plots in d, showing the evolution of vortex-free YSR states into a robust ZBP at 0 T under an approaching-tip. Red arrow in d indicates the position of an accidental near degeneracy of the YSR states. Black circles in d trace the peak positions. e and f are the same as c and d, but measured in a magnetic field of 6 T. Black circles in f trace the peak positions. The accidental degeneracy of the YSR states in 0 T in d is removed by the 6 T magnetic field, while the evolution to the ZBP remains robust. g and h are the same as e and f, but showing the transition from ZBP to YSR states by withdrawing the STM tip at 6 T, indicating the transition is reversible.
