Nanoscale Control over Single Vortex Motion in an Unconventional Superconductor

Abstract

Precise control of superconducting vortices is crucial for studying vortex dynamics and vortex braiding. We propose a new method to pull vortex lines in the multigap superconductor FeSe using a scanning tunneling microscope (STM) tip. Point defects and strain-induced wrinkles act as trapping potentials, deforming vortex lines and altering local vortex lattice configurations. Weak contact of the STM tip with the FeSe surface selectively suppresses the larger superconducting gap while leaving the smaller gap intact, thereby creating a tunable vortex pinning potential. This enables controlled vortex line deformation even in dense vortex lattices. Analytical modeling reveals that the deformation strength scales logarithmically with conductance and depends on tip geometry. Our findings point to local strain–induced gap suppression as the mechanism for STM-mediated vortex manipulation, providing a fundamental insight relevant to vortex behavior in the context of quantum information studies.