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I have just started studying basic solid state physics and I got to know that filled or empty bands do not conduct. Is this only the case for valence band or also conduction band.

Is there any case that I can excite so many electrons to the conduction band that it becomes completely filled and stops conducting?

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  • $\begingroup$ Good question.. I think that it is actually impossible because the conduction band is 'continuous' meaning that there are infinitely many energy states in any given interval of energy states similar ot how we say infinitely many numbers in an interval $\endgroup$ Jan 26 at 10:31
  • $\begingroup$ @Buraian - no, unfilled bands above the Fermi level are still discrete bands, not a continuum. $\endgroup$
    – Jon Custer
    Jan 26 at 14:02
  • $\begingroup$ Is there anything which is a continuum here? I remember reading something like the orbitals mixing and being continous energy levels to obey some quantum law. @JonCuster $\endgroup$ Jan 26 at 14:06
  • $\begingroup$ @Buraian - pick a crystal and look at the band structure (calculated or other) - there are higher, unfilled bands above the conduction band. And, yes, they are bands. $\endgroup$
    – Jon Custer
    Jan 26 at 14:08

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One uses term valence band for the last completely filled band (at zero temperature), and conduction band for the first not fully filled (or empty) band. So, by definition, conduction band is not fully occupied - otherwise it would be a valence band.

Note however that things are not always so clearly cut: see figures here.

This is similar to HOMO and LUMO orbitals in molecular phsyics, which mean

  • HOMO = highest occupied molecular orbital
  • LUMO = lowest unoccupied molecular orbital
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Yes and no. The point is that any conductor has its own "breakpoint". Just consider a fuse. The conductivity is limited by its resistance, after that the material starts to melt or lose energy in some way.

So, yes it stops conducting. But just because it broke up.

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