Eigenvalues may not be always real for generalized eigenvalue problems even if the Hamiltonian and overlap matrices are both Hermitian. When the overlap is associated with a norm of physical state, th...

Bulk-edge correspondence is universal. We do find a novel playground of the chiral edge states protected by bulk topology. It is in the evolutionary game theory realized in a kagome network. The paper...

We are proposing one more lattice structure with frustration that hosts flat bands, square-Kagome lattice. Using a molecular orbital representation, its flat band and flat dispersion only in some spec...

雑誌「固体物理」No.7 (通巻665号)のトピックス欄に助教の溝口知成さんと記事を書きました。溝口知成・初貝安弘　分子軌道表現」を用いた第3種ディラックコーンの統計的構成法。ご覧下さい。

Quantum mechanics tells us particles are waves at the same time. One may then naively expect that the quantum state is extended, especially with translational invariance. However, it is not always tru...

We propose topological semimetals generated by the square-root operation for tight-binding models in two and three dimensions, which we call square-root topological semimetals. The square-root topolog...

Flat bands cannot be accidental. Physically, it implies that the itinerancy of the system is not sufficient. Formal reasons are given by a molecular orbital (MO) representation which we are proposing....

As for topological phases, bulk is usually hidden in the sense that non trivial topological numbers of the bulk are hardly observed directly by standard experiments. Then observation of edge states re...