Occupation probabilities and current densities of bulk and edge states of a Floquet topological insulator

Hossein Dehghani, Aditi Mitra

    Research output: Contribution to journalArticle

    Abstract

    Results are presented for the occupation probabilities and current densities of bulk and edge states of half-filled graphene in a cylindrical geometry and irradiated by a circularly polarized laser. It is assumed that the system is closed and that the laser has been switched on as a quench. Laser parameters corresponding to some representative topological phases are studied: one where the Chern number of the Floquet bands equals the number of chiral edge modes, a second where anomalous edge states appear in the Floquet Brillouin zone boundaries, and a third where the Chern number is zero, yet topological edge states appear at the center and boundaries of the Floquet Brillouin zone. Qualitative differences are found for the high-frequency off-resonant and low-frequency on-resonant laser with edge states arising due to resonant processes occupied with a high effective temperature on the one hand, while edge states arising due to off-resonant processes occupied with a low effective temperature on the other. For an ideal half-filled system where only one of the bands in the Floquet Brillouin zone is occupied and the other empty, particle-hole and inversion symmetry of the Floquet Hamiltonian implies zero current density. However the laser switch-on protocol breaks the inversion symmetry, resulting in a net cylindrical sheet of current density at steady state. Due to the underlying chirality of the system, this current density profile is associated with a net charge imbalance between the top and bottom of the cylinders.

    Original languageEnglish (US)
    Article number205437
    JournalPhysical Review B
    Volume93
    Issue number20
    DOIs
    StatePublished - May 26 2016

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Condensed Matter Physics

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