Tomoki Ozawa

Jan 10, 2025 | nature.com | Tao Chen |Chenxi Huang |Ivan Velkovsky |Tomoki Ozawa |Hannah Price |Jacob P. Covey

AbstractFlat bands in condensed matter systems can host emergent states of matter, from insulating states in twisted bilayer graphene to fractionalized excitations in frustrated magnets and quantum Hall materials. A key phenomenon in certain flat-band systems is Aharonov–Bohm caging, where particles become localized due to destructive interference caused by gauge fields.

Aug 21, 2024 | link.aps.org | Ryo Takahashi |Tomoki Ozawa

In this study, we discuss a type of bulk-boundary correspondence, which holds for topological insulators and superconductors when the parity-time (PT) and/or parity-particle-hole (PC) symmetry are present. In these systems, even when the bulk topology is nontrivial, the edge spectrum is generally gapped, and thus the conventional bulk-boundary correspondence does not hold.

Aug 11, 2023 | link.aps.org | Ryo Takahashi |Tomoki Ozawa

We propose an unconventional bulk-edge correspondence for two-dimensional Stiefel-Whitney insulators and Euler insulators, which are topological insulators protected by the PT symmetry. We find that, although the energy spectrum under the open boundary condition is generally gapped, the entanglement spectrum is gapless when the Stiefel-Whitney or Euler class is nonzero.