The total transmission probability of an asymmetric Aharonov-Bohm ring with an embedded scattering center in both branches and a magnetic flux passing through its center has been investigated. The transmission is calculated from the overall scattering matrix for the ring structure determined by cascading scattering matrices without the symmetric conditions. In this model, by imposing scattering centers with different strengths to the upper and lower arms of the ring, the effects of coupling between the ring and the leads and the magnetic flux in the total transmission probability as a function of transmission phase have been observed. We find the following results from our model study: 1) in the strong coupling limit, there is no zero transmission; 2) with a constant coupling and scatterer in each branch, the transmission peaks get closer together and the transmission becomes smoother as the magnetic flux increases; and 3) in the weak coupling limit with a constant magnetic flux and elastic scattering in each arm, transmission resonances become sharper due to the localized states in the ring and the magnitude of transmission is enhanced at smaller transmission phases.For the case of a single or double barrier in one arm of the ring, the discrete energy levels of the double barrier well in one branch are controlled by the width of the well and continuous levels in the other branch are controlled by a single scattering barrier. We find a peculiar quantum transport through this system such as a symmetric Breit-Wigner (BW) and an asymmetric Fano transmission resonance. The transition from BW to Fano resonance occurs by tuning either the transmission phase of the electrons through a single barrier or the magnetic AB flux threading through the AB ring. The characteristics of the Fano line-shape resonance will be examined by the asymmetric parameter that is a measure of the degree of coupling between the discrete state and the continuum. / Department of Physics and Astronomy
| Identifer | oai:union.ndltd.org:BSU/oai:cardinalscholar.bsu.edu:handle/187646 |
| Date | January 2003 |
| Creators | Ahmadi, Aphrodite |
| Contributors | Joe, Yong Suk |
| Source Sets | Ball State University |
| Detected Language | English |
| Format | vi, 86 leaves : ill. (some col.) ; 28 cm. |
| Source | Virtual Press |
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