Condensed Matter Seminar
June 29 (Thu.) 2023
10:30-11:30 Zoom

Meeting ID: 889 1400 3345
Passcode: 662572

Title:Why monopole becomes dyon in topological insulators

Speaker:Hidenori Fukaya (Osaka University)

The Witten effect predicts that a magnetic monopole acquires a fractional electric charge inside topological insulators. In this work, we give a microscopic description of this phenomenon, as well as an analogous two-dimensional system with a vortex. We solve the Dirac equation of electron field both analytically in continuum and numerically on a lattice, by adding the Wilson term and smearing the gauge field within a finite range to regularize the short-distance behavior of the system. Our results reveal that the Wilson term induces a strong positive mass shift, creating a domain-wall around the monopole/vortex. This small, yet finite-sized domain-wall localizes the chiral zero modes and ensures their stability through the Atiyah-Singer index theorem, whose cobordism invariance is crucial in explaining why the electric charge is fractional. This talk is based on a work in collaboration with Shoto Aoki, Naoto Kan, Mikito Koshino and,
Yoshiyuki Matsuki.