8 papers
Exceptional second-order topological insulators
Yutaro Tanaka, Daichi Nakamura, Ryo Okugawa +1
Point-gap topological phases of non-Hermitian systems exhibit exotic boundary states that have no counterparts in Hermitian systems. Here, we develop classification of second-order…
Hopf Bifurcation of Nonlinear Non-Hermitian Skin Effect
Kohei Kawabata, Daichi Nakamura
The non-Hermitian skin effect, nonreciprocity-induced anomalous localization of an extensive number of eigenstates, represents a hallmark of non-Hermitian topological systems with…
Subspace-Protected Topological Phases and Bulk-Boundary Correspondence
Kenji Shimomura, Ryo Takami, Daichi Nakamura +1
While tremendous research has revealed that symmetry enriches topological phases of matter, more general principles that protect topological phases have yet to be explored. In this…
-theory classification of Wannier localizability and detachable topological boundary states
Ken Shiozaki, Daichi Nakamura, Kenji Shimomura +2
A hallmark of certain topology, including the Chern number, is the obstruction to constructing exponentially localized Wannier functions in the bulk bands. Conversely, other types…
Non-Hermitian Origin of Detachable Boundary States in Topological Insulators
Daichi Nakamura, Ken Shiozaki, Kenji Shimomura +2
While topology can impose obstructions to exponentially localized Wannier functions, certain topological insulators are exempt from such Wannier obstructions. The absence of the Wa…
Non-Hermitian Hopf insulators
Daichi Nakamura, Kohei Kawabata
Hopf insulators represent a unique class of topological insulators that exist exclusively in two-band systems and are inherently unstable upon the inclusion of additional bands. Me…