194 research outputs found
Spin-dependent transport through a chiral molecule in the presence of spin-orbit interaction and non-unitary effects
Recent experiments have demonstrated the efficacy of chiral helically shaped
molecules in polarizing the scattered electron spin, an effect termed as
chiral-induced spin selectivity (CISS). Here we solve a simple tight-binding
model for electron transport through a single helical molecule, with spin-orbit
interactions on the bonds along the helix. Quantum interference is introduced
via additional electron hopping between neighboring sites in the direction of
the helix axis. When the helix is connected to two one-dimensional single-mode
leads, time-reversal symmetry prevents spin polarization of the outgoing
electrons. One possible way to retrieve such a polarization is to allow leakage
of electrons from the helix to the environment, via additional outgoing leads.
Technically, the leakage generates complex site self-energies, which break
unitarity. As a result, the electron waves in the helix become evanescent, with
different decay lengths for different spin polarizations, yielding a net spin
polarization of the outgoing electrons, which increases with the length of the
helix (as observed experimentally). A maximal polarization can be measured at a
finite angle away from the helix axis.Comment: 12 pages, 5 figure
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