Symmetries and Spins in 2D Membranes and Traditional Semiconductors


Add to Cal
  • Speaker: Hanan Dery (University of Rochester)
  • Host Department: Physics
  • Date: 04/23/2013
  • Time: 4:00 PM - 5:00 PM

  • Location: 335 West Hall

  • Description:

    Group theory is a powerful tool to investigate spin-dependent
    transport and optical properties. It allows one to identify important
    processes and to define the physics with a minimal set of material
    dependent parameters. In this talk, I will present our recent findings
    for two material classes.

    Monolayer Transition-Metal Dichalogonides [1]: I will first delineate
    the transport limitations via zeroth-order selection rules and make
    connection with the energy relaxation of electrons, holes and hot
    excitons. Then, I will expand on spin flips induced by flexural
    phonons and show that the spin relaxation is ultrafast for electrons
    in free-standing membranes while being mitigated in supported
    membranes. This behavior is universal in 2D membranes that respect
    mirror symmetry and it leads to a counterintuitive inverse relation
    between mobility and spin relaxation. The findings will be compared
    with the case of graphene.

    Group IV semiconductors [2-6]: These materials are ideal choices for
    spintronic devices due to their relatively long spin lifetimes and
    mature technology. I will present our findings on the effects of
    electron-phonon interaction on spin-dependent optical and transport
    properties in Si and Ge.

    [1] Y. Song and H. Dery, “Transport Theory of Monolayer
    Transition-Metal Dichalcogenides”, preprint: arXiv 1302.3627 (2013).
    [2] P. Li, D. Trivedi and H. Dery, “Spin-dependent optical properties
    in strained silicon and germanium”, Phys. Rev. B 87, 115203 (2013).
    [3] P. Li, Y. Song and H. Dery, “Intrinsic spin lifetime of conduction
    electrons in germanium”, Phys. Rev. B 86, 085202 (2012).
    [4] J. Li, L. Qing, H. Dery, and I. Appelbaum, “Field-induced negative
    differential spin lifetime in silicon”, Phys. Rev. Lett. 108, 157201
    [5] P. Li and H. Dery, “Spin-Orbit Symmetries of Conduction Electrons
    in Silicon”, Phys. Rev. Lett. 107, 107203 (2011).
    [6] P. Li and H. Dery, “Theory of spin-dependent phonon-assisted
    optical transitions in silicon”, Phys. Rev. Lett. 105, 037204 (2010).