At high temperatures, current tends to be less because the electron motion is less organized, more random.
At their heart, surface plasmon polaritons are a combination of light waves and electron motion.
Since the electron motion is in phase with the field of the light already emitted, the fields add together coherently.
Or one might ask, does the electron motion define the probability solution?
In this model, the observed phenomena are explained as the effects of the electron motions on the electromagnetic field, called the source field effect.
This net electron motion is usually much slower than the normally occurring random motion.
Werner Heisenberg develops the uncertainty principle which, among other things, explains the mechanics of electron motion around the nucleus.
The angle at which the light hits the interface means that some of the light's electric field can drive electron motion along the surface.
Because the electron carries negative charge, the electron motion in a metal conductor is in the direction opposite to that of conventional (or electric) current.
I cannot think of any reason the electric field could constrain electron motion.