ISSP - The institute for Solid State Physics

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Oka Group
Professor
OKA,
Takashi

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 materials. The target materials range from topological systems to strongly correlated systems (Fig.1). New non-linear response phenomena such as the heterodyne Hall effect (Fig.2), i.e. quantum Hall effect induced by oscillating magnetic fields, will be studied as well.

Fig. 1. Floquet engineering in quantum materials. T. Oka, S. Kitamura, Annu. Rev. Condens. Matter Phys. 10, 387-408 (2019).
Fig. 2. Heterodyne device utilizing Floquet states. (a) Frequency mixed output is realized. (b) A realization of the heterodyne Hall effect using 2D Dirac semimetals.

Research Subjects

  1. Floquet engineering of quantum materials
  2. Fundamental research on phase transition in nonequilibrium quantum systems
  3. Proposal of novel nonlinear quantum devices