## Surprises on the nanoscale: Plasmonic waves that travel backward and spin birefringence without magnetic fields

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#### Abstract

As nanonphotonics and nanoelectronics are pushed down towards the molecular scale, interesting effects emerge. We discuss how birefringence (different propagation of two polarizations) is manifested and could be useful in the future for two systems: coherent plasmonic transport of near-field light and spin-birefringence.

We first show that a very simple dipole-coupling model, valid for coherent transport on small scales, predicts that the different polarizations of near-field light can travel in opposite directions, i.e., with one of them having a negative refraction index. More importantly, at special velocities a "conical intersection"-like phenomena occurs, with very easy scattering from one polarization to the other. Therefore, the light direction could be changed abruptly, leading hopefully to interesting future devices

The second part of the talk discusses simulations of control of spin-current on the molecular scale without using magnetic fields. Spin-orbit effects coupled with a circular geometry make an electron with spin up capture a different phase then an electron with spin down; a simulation of a transport through (acetylene-bitellurium-naphthalene)9 shows that this effect can be used to flip the spin of an initially polarized electron, and the flipping is controlled by the injection energy of the electron.

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WTHR 201