Accueil > Agenda Scientifique

Les événements de juillet 2019

séminaire

<p>séminaire</p>
  • Séminaire des doctorants

    • Jeudi 11 juillet 11:00-12:00 - Alexander Zyuzin - Aalto University, Helsinki

      Collective mode in metals with spin or valley population imbalance

      Résumé : The effect of electron-electron exchange interaction in metals with non-equilibrium spin orientation will be first reviewed. It will be shown,that, as a result of the interaction, there exists a spin wave mode, describing the spin precession in the absence of applied magnetic field. The dispersion relation of the mode is gapless, proportional to the square of the wavevector at small frequencies, and inversely proportional to the electron-electron exchange interaction energy. The valley wave analog will be then discussed for the case of metals with valley population imbalance. Doped graphene and three-dimensional Weyl-Dirac semimetals will be considered as particular material candidates. The spin and valley waves serve as the energy gain sources for the external field, that generates the spin or inter-valley transitions.

      Lieu : LPS, bât 510, salle 208a, aîle sud

      Article

  • Séminaire des doctorants

    • Mardi 16 juillet 11:00-12:00 - Claudio Chamon - Boston University

      Braiding Light

      Résumé : Many topological phenomena first proposed and observed in the context of electrons in solids have recently found counterparts in optical and acoustic systems. In this talk we will discuss non-Abelian Berry phases that can accumulate when coherent states of light are injected into "topological guided modes" in specially-fabricated photonic waveguide arrays. These modes are photonic analogues of topological zero modes in electronic systems. Light traveling inside spatially well-separated topological guided modes can be braided, leading to the accumulation of non-Abelian phases, which depend on the order that the guided beams are wound around each other. Notably, these effects survive the macroscopic photon occupation limit, and can be understood as wave phenomena and thus predicted directly from Maxwell’s equations without resorting to quantization of light.

      Lieu : LPS, bât 510, salle 208a, aîle sud

      Article

Ajouter un événement