On Dec. 18, 2019, Yuichi Otsuka (RIKEN) will tell us on their work of the quantum Monte Carlo study for interacting Dirac fermions on lattice. As is known, the Dirac fermions are mother of all topological phases. " QMC Study of quantum criticality in 2D interacting Dirac fermions.". The talk will be given in Japanese.

On Dec. 11 (Wed), K. Kawaguchi (RIKEN) will tell us on their work by a title "Collective cell dynamics and topology". It's a new area for us. Join the seminar. The talk will be given in Japanese.

We have discussed a non-hermitian version of the fractional quantum Hall states. The paper, by Tsuneya Yoshida, Koji Kudo and Yasuhiro Hatsugai, has been published in Scientific Reports ( also arXiv:1907.07596 ). Non-hermitian physics has been extended to the topologically ordered states. It's a try. Relevant situations can be realized in cold atom experiments.

Covalent Organic Frameworks (COF), I understand, is a large molecule where many (block) organic molecules are linked by strong covalent bonds in a periodic or non-periodic manner. It is a nice place where the higher order topological insulating phase is realized as we have pointed out. Then if the COF has boundaries, one can naturally expect edge states/corner states associated with the symmetry protected Berry phases of the bulk. This is correct. One of such a COF, we discussed, is a polymerized triptycene on a decorated star lattice. Our paper ”Flat bands and higher-order topology in polymerized triptycene: Tight-binding analysis on decorated star lattices” by Tomonari Mizoguchi, Mina Maruyama, Susumu Okada, Yasuhiro Hatsugai is for the phenomena and has been published in Physical Review Materials (See also arXiv 1907.06088).

We have proposed a new correlated topological phase, "higher-order topological Mott insulator (HOTMI)" where spin-charge separated corner states emerge that are protected by Z₃ spin Berry phases of the bulk. It is a generalized bulk-edge correspondence. The article has been published in Phys. Rev. Lett. (also arXiv:1905.03484). Have a look at.