80 research outputs found
Electron transport in an open mesoscopic metallic ring
We study electron transport in a normal-metal ring modeled by the tight
binding lattice Hamiltonian, coupled to two electron reservoirs. First,
Buttiker's model of incorporating inelastic scattering, hence decoherence and
dissipation, has been extended by connecting each site of the open ring to
one-dimensional leads for uniform dephasing in the ring threaded by magnetic
flux. We show with this extension conductance remains symmetric under flux
reversal, and Aharonov-Bohm oscillations with changing magnetic flux reduce to
zero as a function of the decoherence parameter, thus indicating dephasing in
the ring. This extension enables us to find local chemical potential profiles
of the ring sites with changing magnetic flux and the decoherence parameter
analogously to the four probe measurement. The local electrochemical potential
oscillates in the ring sites because of quantum-interference effects. It
predicts that measured four-point resistance also fluctuates and even can be
negative. Then we point out the role of the closed ring's electronic
eigenstates in the persistent current around Fano antiresonances of an
asymmetric open ring for both ideal leads and tunnel barriers. Determining the
real eigenvalues of the non-Hermitian effective Hamiltonian of the ring, we
show that there exist discrete bound states in the continuum of scattering
states for the asymmetric ring even in the absence of magnetic flux. Our
approach involves quantum Langevin equations and non-equilibrium Green's
functions.Comment: 19 pages, 6 figure
Bound states in the continuum in open Aharonov-Bohm rings
Using formalism of effective Hamiltonian we consider bound states in
continuum (BIC). They are those eigen states of non-hermitian effective
Hamiltonian which have real eigen values. It is shown that BICs are orthogonal
to open channels of the leads, i.e. disconnected from the continuum. As a
result BICs can be superposed to transport solution with arbitrary coefficient
and exist in propagation band. The one-dimensional Aharonov-Bohm rings that are
opened by attaching single-channel leads to them allow exact consideration of
BICs. BICs occur at discrete values of energy and magnetic flux however it's
realization strongly depend on a way to the BIC's point.Comment: 5 pgaes, 4 figure
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