Propagation in a Crystal Lattice: Feynman's Physics Explained
How does an electron move through the perfectly regular lattice of a crystal? It has some amplitude to tunnel, or hop, from one atom to the next, and this coupling means the true stationary states are not electrons stuck on single atoms but wavelike states spread across the whole crystal. These electron waves can take a continuous range of energies within certain allowed 'energy bands.'
The big idea
In a crystal, electrons spread into waves filling allowed energy bands.
Think about it
Why does an electron in a regular crystal end up belonging to the whole crystal rather than to one atom?
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