5 papers
Quantum geometric ferromagnetism by singular saddle point
Taisei Kitamura, Hiroki Nakai, Akito Daido +1
We propose ferromagnetism that occurs in electrons at a saddle point with band touching, which we call the singular saddle point. At the singular saddle point, the divergent quantu…
Spin-orbital exchange as a route to intertwined dipole-quadrupole orbital order in MnVO under strong trigonal crystal field
Hiroki Nakai, Yusuke Nomura
Orbitally degenerate systems provide a promising platform for realizing novel quantum phases driven by spin-orbital exchange interactions, as described by the Kugel-Khomskii model.…
Quantum-geometry-driven exact ferromagnetic ground state in a nearly flat band
Taisei Kitamura, Hiroki Nakai, Hosho Katsura +1
We construct a Hubbard model with a nearly flat band whose quantum geometry can be tuned independently of the energy dispersion and the Coulomb interaction. We show that, when the…
Spin amplitude wave due to dipole-quadrupole hybridization in spin-1 pyrochlore magnets
Hiroki Nakai, Chisa Hotta
We explore the quantum pseudospin-1 pyrochlore magnet featuring Fe-based spinel oxides that addresses the formation of amplitude-modulated spin-density waves. We propose tha…
Spinor ice correlation in flat-band electronic states on kagome and pyrochlore lattices with spin-orbit coupling
Hiroki Nakai, Masafumi Udagawa, Chisa Hotta
We investigate the emergence and transformation of pinch-point singularities in the excitation spectrum of electronic flat band systems on kagome and pyrochlore lattices with spin-…