Document Type thesis Author Name Li, Zehao URN etd-032913-134839 Title Quantum Mechanics on the Möbius Ring Degree MS Department Physics Advisors L. R. Ram-Mohan, Advisor Germano Iannacchione, Committee Chair Keywords finite element method Aharonov-Bohm effect half-integer angular momentum Möbius ring Date of Presentation/Defense 2013-02-04 Availability restricted
Recent advances in the chemical vapor deposition method of growing graphene sheets suggest that graphene rings can grow. We may anticipate that chemical methods can be developed to construct twisted nano-ribbons to form MÃ¶bius structures in the very near future. I investigated the quantum mechanics of an electron constrained to motion on a nanoscale MÃ¶bius ring by solving the Schrdinger equation on the curved surface. The close analogy between ordinary cylindrical rings and MÃ¶bius rings is displayed by the closeness of their energy spectra. The expectation values for the angular momentum component L_z are shown to be close, but not exactly equal, to integral or half-integral multiples of hbar. The half-integer angular momentum states are present only for the nontrivial topology of MÃ¶bius rings. The effect of the curvature of the MÃ¶bius rings manifests itself in the level splitting. This can be understood in terms of representations of the discrete rotational groups C_nv. The nonzero variance of L_z will allow weak transitions between integral and half-integral angular momentum states, while preserving the unit angular momentum for photons.
Again, since the topology of the system is critical for the Aharonov-Bohm effect, I investigated the AB effect on MÃ¶bius rings and found a remarkable pattern in transmission through finite-width 2D ring structures with finite-width input and output contacts attached at the periphery. The periodicity in the magnetic flux, in units of h/e, is weakly broken on 2D rings of finite width. The unusual states with half-integer values of
observed on MÃ¶bius rings, investigated earlier, display a different characteristic in transmission.
In view of the fascinating properties displayed by the non-trivial topology in terms of its novel two-dimensional physics, we expect that the properties of carriers on the MÃ¶bius ring that we have presented here will be relevant for practical applications.
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