62nd CEMS Colloquium

講演者

川上 則雄 (京都大学 教授)

日程

2018年6月27日(水) 17:30~18:30

開催場所

理化学研究所 大河内ホール

講演タイトル

強相関系におけるレーザー誘起トポロジカル相

講演概要

We discuss emergent topological phases induced by laser irradiation in correlated electron (fermion) systems.

We first address a possible way to realize topological superconductivity with application of laser light to superconducting cuprate thin films. Applying Floquet theory to a model of d-wave superconductors with Rashba spin-orbit coupling, we derive an effective model and discuss its topological nature. Interplay of the Rashba spin-orbit coupling and the laser light effect induces the synthetic magnetic fields, thus leading to a topological superconductor characterized by a Chern number. The effective magnetic fields do not create the vortices in superconductors, and thus the proposed scheme provides a promising way to realize a topological superconductor in cuprates [1].

We then study the nature of laser-irradiated Kondo insulators. We find two generic effects induced by laser light. One is the dynamical localization, which suppresses hopping and hybridization, and the other is the laser-induced hopping and hybridization, which can be interpreted as a synthetic spin-orbit coupling or magnetic field. In topological Kondo insulators, linearly polarized laser light realizes phase transitions between trivial, weak topological and strong topological Kondo insulators, whereas circularly polarized laser light breaks time-reversal symmetry, thereby inducing Weyl semimetallic phases [2].

If time allows, we also address topological phase transitions in correlated fermions in optical lattices. Laser induced Kondo effect newly proposed for cold atoms can be used for discussing symmetry-protected Kondo insulating phases and topological phase transitions among them [3].

References
[1] K. Takasan, A. Daido, N. Kawakami, Y. Yanase. Phys. Rev. B 95, 134508 (2017).
[2] K. Takasan, M. Nakagawa, N. Kawakami, Phys. Rev. B 96, 115120 (2017).
[3] M. Nakagawa and N. Kawakami, Phys. Rev. Lett. 115, 165303 (2015); Phys. Rev. B 96, 155133 (2017)