How can I distinguish degeneracy from band structure?

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    Degeneracy Valence band
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Discussion Overview

The discussion centers on distinguishing degeneracy in band structure, particularly at the gamma point, and whether degeneracy is solely related to the crossing of valence and conduction bands or can occur in other contexts, such as touching bands.

Discussion Character

  • Debate/contested

Main Points Raised

  • Some participants propose that bands are considered degenerate when they cross or touch at the gamma point.
  • Others question whether degeneracy is only relevant when the valence and conduction bands cross, or if it can also apply to touching valence or conduction bands.
  • One participant asserts that conduction bands are degenerate at the gamma point due to coalescence, while valence bands cross without degeneracy because they are separated by a band gap.
  • Another participant seeks clarification on whether a band structure can be termed degenerate if there is a crossing in the valence bands alone, independent of the conduction bands.

Areas of Agreement / Disagreement

Participants express differing views on the conditions under which degeneracy is defined, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

The discussion includes assumptions about the definitions of degeneracy and band structure, and the implications of band crossings and separations, which are not fully explored or agreed upon.

Mohammad-gl
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TL;DR
I have a band structure plot and want to know if it is degenerated or non-degenerated. How can I realize that?
This is the band structure.
Untitled.png
 
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Where the bands cross or touch at the gamma point, they are degenerate.
 
Dr Transport said:
Where the bands cross or touch at the gamma point, they are degenerate.
In fact my question is that the degeneracy is related to cross the valence and the conduction band or that can be happen even in touching the valences or conduction bands too?
 
Mohammad-gl said:
In fact my question is that the degeneracy is related to cross the valence and the conduction band or that can be happen even in touching the valences or conduction bands too?
I don't understand your response. The conduction bands are degenerate at the gamma point because they coalesce. The valence bands cross at the gamma point, because they cross. the conduction and valance bands are not degenerate in this case because they are completely separated by the band gap, plain and simple.
 
Dr Transport said:
I don't understand your response. The conduction bands are degenerate at the gamma point because they coalesce. The valence bands cross at the gamma point, because they cross. the conduction and valance bands are not degenerate in this case because they are completely separated by the band gap, plain and simple.
I mean that generally can we call a band structure degenerate even if there be a cross in the valence bands? and is not crucial that valence and conduction bands cross each other?
 

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