Oshikawa Group

Professor

OSHIKAWA,Masaki

Research Associate

TADA,Yasuhiro

Our main focus is quantum many-body theory. Based on the close correspondence among quantum many-body systems, classical statistical systems, and field theory, we pursue universal concepts in physics. At the same time, we aim to give a unified picture on experimental data and to make testable predictions. As an example of our recent achievements, we have given a certain theoretical result for the total orbital angular momentum of chiral superfluids, which has remained paradoxical for 40 years. We also demonstrated, based on anomaly in quantum field theory, a new classification of gapless quantum critical phases in the presence of a discrete symmetry. This opens up a new direction in classification of quantum phases. In order to connect these theoretical developments with experiments, we also study material design to realize exotic topological phases such as Kitaev spin liquids. Much of our research is carried out in international collaborations.

Designing Kitaev spin liquid using Metal-Organic Framework (MOF). Kitaev model is an intriguing exactly solvable spin model, with a spin-liquid ground state. Although realizations of the Kitaev model in iridates and other inorganic materials has been discussed, the dominance of Heisenberg type interactions owing to direct exchanges prevents the ground state from becoming the spin liquid. We proposed a possibility of more ideal realizations of the Kitaev model, using MOFs in which direct exchange interactions are suppressed.

- Electron Spin Resonance in quantum spin systems and itinerant electron systems
- Conduction at a junction of quantum wires and conformal field theory
- Topological phases and quantum entanglement
- Orbital angular momentum of chiral superfluids
- Realization of topological phases and topological phenomena in materials

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Construction of Hamiltonians by supervised learning of energy and entanglement spectra: H. Fujita, Y. O. Nakagawa, S. Sugiura and M. Oshikawa, Phys. Rev. B **97** (2018) 075114 (1-12).

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Theoretical study on volume law of Rényi entanglement entropy in quantum many-body systems: Y. Nakagawa, The University of Tokyo (2018).

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Fulde-Ferrell state in a ferromagnetic chiral superconductor with magnetic domain walls: Y. Tada, Physical Review B **97** (2018) 014519.

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「量子スピン液体」の神秘性 – 宇宙と物質のあいだにある不思議な対応関係とは: 山田 昌彦, academist Journal (2018) 6995.

^{†} Joint research with outside partners.