Prof. Gil Young Cho (POSTECH)
"Many-Body Invariants for Multipoles in Higher-Order Topological Insulators"
We propose many-body invariants for multipoles in higher-order topological insulators by generalizing Resta's pioneering work on polarization. The many-body invariants are designed to measure multipolar charge distribution in a crystalline unit cell, and they match the localized corner charge originating from the multipoles. We provide analytic arguments and numerical proof for the invariants. Furthermore, we show that the many-body invariants faithfully measure the physical multipole moments even when the nested Wilson loop approaches fail to do so.