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Oka Group

member
Professor OKA, Takashi
Affiliation
Functional Materials Group
(concurrent with Division of Condensed Matter Theory)
Course
Phys., Sci.
Group's HP
Research Associate NUMASAWA, Tokiro
Project Research Associate OKUMURA, Shun

Research Subjects

  • Floquet engineering of quantum materials
  • Phase transitions in nonequilibrium systems
  • Application of field theory to biology and information physics

Our main research subject is quantum materials driven far away from equilibrium by external fields such as laser light. The aim is to seek for new laws of physics that govern such exotic states and to find a way to control their collective dynamics. We employ new theoretical frameworks such as Floquet engineering which enables us to understand nonequilibrium physics with the depth comparable to equilibrium systems. We can also obtain important insights from other existing research fields such as turbulence, neural network, and non-linear semiconductor optics, and apply them to new exotic quantum materials. The target materials range from topological systems to strongly correlated systems (left figure). New non-linear response phenomena such as the heterodyne Hall effect (right figure), i.e. quantum Hall effect induced by oscillating magnetic fields, will be studied as well. We are also interested in problems outside of the traditional condensed matter physics, such as chemical reaction networks in biological systems and information theory.

Floquet engineering in quantum materials. T. Oka, S. Kitamura, Annu. Rev. Condens. Matter Phys. 10, 387-408 (2019).
Heterodyne device utilizing Floquet states. (a) Frequency mixed output is realized. (b) A realization of the heterodyne Hall effect using 2D Dirac semimetals.

Publications and Research Highlights