Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 80: Low-Dimensional Systems - Poster Session

TT 80.3: Poster

Wednesday, April 2, 2014, 15:00–19:00, P2

Polaritons in a Quantum Spin Hall Insulator — •Alexander Janot¹, Bernd Rosenow¹, and Gil Refael² — ¹Institut für Theoretische Physik, Universität Leipzig, 04009 Leipzig, Germany — ²Department of Physics, California Institute of Technology, Pasadena, CA 91125, USA

We study the topological properties of mixed matter-light particles, so called polaritons, in a quantum spin hall insulator coupled to photonic cavity modes. Taking into account the spin and polarization structure of electrons and photons, respectively, we find that the electron-photon coupling matrix can be characterized by a non-trivial pseudo-spin vector. For a topological quantum spin hall system this vector wraps around the Bloch sphere twice as the wave vector covers the entire Brillouin zone, while the winding number is zero in the topologically trivial case. We find that the Hilbert space spanned by the two lower polariton branches is no longer degenerate as in the absence of spin-orbit coupling, and exhibits a pseudo-spin vector which is constraint to the x-y plane. This picture changes for the case of a chiral cavity supporting only one polarization. Focusing on the lower polariton branch, the excitonic components of the polaritons are characterized by a non-trivial pseudo-spin vector. This findings suggest a possible variety of new topological phenomena in coupled light-matter systems.