Modeling Image Potential States on Topological Semimetal Antimony Surface*

Topological materials host protected surface states with locked spin and momentum degrees of freedom that are predicted to give rise to exotic excitations such as Majorana fermions and magnetic monopoles. The topological semimetal antimony (Sb) offers a pristine platform in which to search for these excitations. Here we present scanning tunneling spectroscopy (STS) studies of Sb at high energy where quantized image potential states form due to the binding between the tunneling electron and the polarized surface. We fit the energies of these quantized states using a one-dimensional model based on the image potential on metal surfaces, the electric field applied between tip and sample, and the work functions of both tip and sample materials. The model fits well with the experimental data as a function of tip-sample voltage and distance. The study of these image potential states allows exploration of the image charge geometry necessary to realize a magnetic monopole.