Circular dichroism measures the chirality of
electronic transitions. You need a circularly polarized beam of
photons to do it.
Would it be possible to use electrons instead of photons? The commonsense
answer is: Yes, but you need spin polarized electrons:
We say: Yes, but you can do it in a regular transmissioen
electron microscope. You need no exotic electrons, nor a synchrotron.
No one tried it before. So we decided to do it.
It will not be an easy task.
What is it good for?
The general objective of CHIRALTEM is to prove
that circular dichroism can be observed in the transmission electron
microscope (TEM) by a novel technique, and thus open a completely
new path for studying and characterising magnetic materials. The
expected results of the project are a) the experimental verification
of a predicted phenomenon in electron scattering; and b) establishing
a new method for the characterization of materials, thus pushing
European technology in the growing field of spintronics. It will
complement the XMCD applications at synchrotrons and provide new
insights for physics and materials science.
The idea is to measure the mixed dynamic form
factor (MDFF) of a chiral electronic transition. Under particular
conditions (violation of time reversal symmetry) the MDFF shows
asymmetry with respect to handedness.