Re: [Phys-l] solid state physics

[Stefan Jeglinski <jeglin@4pi.com>]

>  Yet even the electron with "only one mass" has a different 
> *effective* mass depending on the band structure.  Since the light 
> and heavy hole effective masses arise from motion in different 
> directions within the crystal why doesn't the same thing happen to 
> the electron?

If you're talking effective mass, then you are no longer referring to 
an electron per se, but to yet another pseudoparticle, pretty much by 
definition. A polaron would be an example of the "same thing 
happening to an electron," although it suffers in comparison because 
it is a state involving the underlying crystal structure.

There is only one electron, and one electron mass, and it is not 
"effective." It is the fundamental "real" particle in the story. As 
soon as something is referred to as having an effective mass, it is a 
pseudoparticle.

Keep in mind that electrons, promoted to the conduction band, are 
often described as "nearly free." As such, they come closest to a 
real free electron, and possess properties closest to same. But they 
exist in a band structure, and so are not truly free, and so have 
some effective mass. Terminology being what it is though, they retain 
their "electron" moniker. Holes, OTOH, are grossly not the same thing 
as a "positive electron," and deserve their own name.


Stefan Jeglinski