plxmny said:
I am interested in measuring the effects of a magnetic field on an electron in a tunneling state. I know very little about solid state and I have very little experimental experience.
In order to learn what is required to perform such an experiment, I thought I would pose my question here:
How can one demonstrate experimentally that tunneling electrons are affected by a magnetic field?
Your question is not easily answered AS IS, and I will tell you why.
What you intended to do here is something like this. Have two metals sandwiching an insulating barrier that is the tunnel barrier. You then want to apply a magnetic field JUST TO THE BARRIER to see how the tunneling process is affected by it.
This isn't trivial to do. In fact, it is extremely difficult because
(i) the coherence length is often very short (order of 10's of nanometers) for a charge carrier in metals. So you have to make the insulating barrier rather thin;
(ii) because of (i), it is almost IMPOSSIBLE to "focus" a magnetic field JUST ON THE BARRIER. Inevitably, you will have the whole contraption, and certainly a large part of the metal itself, under a magnetic field. You now can't tell if any changes in measurement is due to just the tunneling process being affected by the magnetic field, or is the magnetic field also affecting the non-tunneling charges in the metals, even if it can only penetrates up to the skin depth into the metals.
So what do we normally do to investigate how magnetic field can in fact influence of magnetic field in the tunneling process? We make insulating barrier that have magnetic moments. Oxides such as Cr2O3, etc. have magnetic moments that can interact with the tunneling particles. Such experiments have shown a very different tunneling spectroscopy, especially in the current versus voltage curve (IV curves), where the "background" shows a linearly increasing curve instead of the "flat" ones that are typically observed. This observation has been attributed to the inelastic scattering of the tunneling particles with the magnetic barrier[1]. In a non-magnetic barrier, most of the particles tunnel through ballistically.
Zz.
[1] J.R. Kirtley and D.J. Scalapino, Phys. Rev. Lett. v.65, p.798 (1990).
