Browsing by Subject "Asymmetric coupling"

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    Spin filtering in a quantum ring with Rashba coupling
    (IEEE, 2010) Tanatar, Bilal; Moldoveanu V.
    We study the effect of Rashba spin-orbit coupling on the spin interference in a non-interacting one-dimensional ring connected to two lead theoretically within the non-equilibrium Greens' function formalism. We compute the charge and spin currents and analyze their Aharonov-Bohm oscillations. The geometry of the system is conveniently described by the angle δ between the two leads. We show that for δ=180° (i.e for symmetrically coupled leads) a good tutering of up or down spin orientation is obtained around half-integer multiples of Φ/Φ0. These particular flux values correspond to degeneracy points for clockwise and counter-clockwise propagating state related to the same spin orientation in the local spin frame of the ring. In contrast, for the asymmetric coupling, i.e., δ=135° the filter efficiency is maximum around integer multiples of Φ/Φ0. The numerical results suggest that the spin filtering is obtained when the clockwise or counter-clockwise states interfere destructively. The spin filtering regime is stable against variations of the bias applied on the system. ©2010 IEEE.
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    Two-dimensional complex parity-time-symmetric photonic structures
    (American Physical Society, 2015-02) Turduev, M.; Botey, M.; Giden, I.; Herrero, R.; Kurt, H.; Özbay, Ekmel; Staliunas, K.
    We propose a simple realistic two-dimensional complex parity-time-symmetric photonic structure that is described by a non-Hermitian potential but possesses real-valued eigenvalues. The concept is developed from basic physical considerations to provide asymmetric coupling between harmonic wave components of the electromagnetic field. The structure results in a nonreciprocal chirality and asymmetric transmission between in- and out-coupling channels into the structure. The analytical results are supported by a numerical study of the Bloch-like mode formations and calculations of a realistic planar semiconductor structure. © 2015 American Physical Society.