****************CTC Condensed Matter Seminar  ****************

Speaker: Prof. Yasuhiro Tada (Hiroshima U, U Tokyo)

Title: Many-body multipole index and bulk-boundary correspondence.

Date/Time: 2023-07-26 / 14:00 - 15:30

Place: P512 of CTC, 5F, 3rd General Building, NTHU.

Host: Prof. Po-Yao Chang (Department of Physics, NTHU)
 

Abstract:
We propose new dipole and quadrupole indices for interacting insulators with point group sym-metries. The proposed indices are defined in terms of many-body quantum multipole operators combined with the generator of the point group symmetry. Unlike the original multipole opera-tors, these combined operators commute with Hamiltonian under the symmetry and therefore their eigenvalues are quantized. This enables a clear identification of nontrivial multipolar states. We calculate the multipole indices in representative models and show their effectiveness as order pa-rameters. Furthermore, we demonstrate a bulk-boundary correspondence: a non-zero index implies the existence of edge/corner states under the point group symmetry.

Reference: arXiv:2302.00800

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