# Do EM waves transmit spin polarization?

Suppose you have a normal dipole antennae (transmitter and receiver) . Spin polarized current (as opposed to normal current) is sent into the transmitter, it emits an EM wave and the Receiver receives it. Will the charge carriers in the receiver become spin polarized as well? In other words, will the spin polarization of the transmitter current have some effect on the receiver, like for example imposing the spin polarization on the receiver carriers by means of making EM radiation circularly polarized?

I am aware that this effect is possible using certain semiconductors. But I am talking about a normal metal chunk used as the antennae. I am wondering whether the spin polarization of the transmitter current will have any effect on the receiver on a deeper level: using principles of Quantum Field Theory and Quantum Electrodynamics? (I don't know anything about QFT and QED btw)

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If the receiver is made of a non-ferromagnetic conductor, it might not support a spin-polarized current even if the EM radiation does carry angular momentum in its polarisation. The electrons would pick up some net spin at first, but that net spin polarisation could well dissipate in transverse phonons or a similar carrier. I'm not sure about the specifics so this might not answer your question, but this mechanism would depend on the electron-transverse phonon coupling in the antenna material. –  Chay Paterson Mar 31 '13 at 16:32
Yes, I beleive spin relaxation is short in non-FMs. What about free charges? I am wondering about the fundamental mechanism of how spin is transferred from a bunch of free charges at the transmitting end to the same at the receiving end. (via radiation of course) –  user1800 Apr 1 '13 at 0:23
I'm not quite sure what you're asking, but the relevant changes in quantum numbers would be: transmitter electron emits photon (electron ms = +1/2 --> -1/2, photon has ms = +1), receiver electron absorbs photon (electron ms = -1/2 --> +1/2). The rates of emission and absorption will depend on DOS in the transmitter and receiver materials. –  Chay Paterson Apr 2 '13 at 19:34
The $m_s = -1/2$ electrons just wouldn't absorb those photons. Conservation of angular momentum forces a selection rule there. –  Chay Paterson Apr 8 '13 at 12:11
@LubošMotl has a good description in his blog on how classical fields emerge from the quantum substrate, and uses the photons as an example motls.blogspot.com/2011/11/… . I am not able to extend the discussion to polarizations from spins. I suspect that "it ain't simple" and will involve assumptions about spatial coherence of spin operators. –  anna v Apr 16 '13 at 4:11