Detection of magnetic monopole in image potential states of topological insulators

Abstract: Magnetic monopoles, hypothetical particles behaving as isolated magnetic charges, have long been predicted by theories beyond the standard model but remain elusive in experimental detection. In this study, we demonstrate a novel method to induce and detect magnetic monopoles on the surface of three-dimensional (3D) topological insulators (TIs) using scanning tunneling microscopy (STM). By applying a radially distributed electric field via the STM tip to induce an image magnetic monopole using the topological magnetoelectric (TME) effect, we observe electric field-dependent intrinsic splitting peaks of image potential states (IPS) on the surface of a 3D high-order TI Bi(111). These IPS splitting phenomena originate from the Zeeman effect of the orbital magnetic moments interacting with the magnetic field generated by the magnetic monopoles. Our experimental results, supported by theoretical modeling, successfully demonstrate the detection of magnetic monopole. This work not only deepens our understanding of topological field theory and axion insulators but also opens new avenues for detecting and manipulating magnetic monopoles. The findings suggest that similar studies can be extended to other topological insulator systems, offering potential applications in quantum computing and novel electronic devices.