1.3k citations · 1.4k across the 5 of their papers we have counts for
9 papers
Time-crystalline long-range order in squeezed ground state
Nobuyuki Okuma
It is widely believed that ground-state time crystals are not realizable in realistic macroscopic systems. In particular, Watanabe and Oshikawa proved a theorem that implies the ab…
Nontrivial interband effect: applications to magnetic susceptibility, nonlinear optics, and topological degeneracy pressure
Nobuyuki Okuma
The interband effect is an important concept both in traditional and modern solid-state physics. In this paper, we present a theory of the nontrivial interband effect, which cannot…
Quantum anomaly, non-Hermitian skin effects, and entanglement entropy in open systems
Nobuyuki Okuma, Masatoshi Sato
We investigate the roles of non-Hermitian topology in spectral properties and entanglement structures of open systems. In terms of spectral theory, we give a unified understanding…
Hermitian zero modes protected by nonnormality: Application of pseudospectra
Nobuyuki Okuma, Masatoshi Sato
Recently, it was established that there exists a direct relation between the non-Hermitian skin effects, -strong dependence of spectra on boundary conditions for non-Hermitian Hami…
Non-Bloch band theory of non-Hermitian Hamiltonians in the symplectic class
Kohei Kawabata, Nobuyuki Okuma, Masatoshi Sato
Non-Hermitian Hamiltonians are generally sensitive to boundary conditions, and their spectra and wave functions under open boundary conditions are not necessarily predicted by the…
Topological Origin of Non-Hermitian Skin Effects
Nobuyuki Okuma, Kohei Kawabata, Ken Shiozaki +1
A unique feature of non-Hermitian systems is the skin effect, which is the extreme sensitivity to the boundary conditions. Here, we reveal that the skin effect originates from intr…