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Re: [Phys-l] solid state physics



Why aren't there light and heavy electrons just as there are light and heavy holes?

An electron is just an electron, so it has only one mass. A hole, although generally described as an electron analog with an opposite charge, is actually better described as an entire electron (valence) band, minus one electron (which has been promoted to the conduction band). Hence the hole's "positive" charge. And, since the hole is actually an entire band of electrons, minus one, its "mass" is typically much larger in magnitude.

The "band" is a solid-state concept, and doesn't generally exist without the presence of a lot of electrons, eg in a crystal. The band structure depends a great deal on the [crystal] environment, so you can imagine the variance that is possible. When an electron is promoted to the conduction band, a variety of holes can be created. Commonly though, there are 2 valence bands of importance, denoted "light" and "heavy," due in part to different transport properties possessed when an electron is lost to the conduction band.

This is basically Solid State 101, and I've glossed over quite a bit. It can get as complicated as you like. The only "real" particle in this field is an electron. But there are plenty of pseudoparticles, of which the hole is one (the polaron is another). With our limited minds, these pseudoparticles serve useful pedagogical and calculational purposes.


Stefan Jeglinski