Band Theory of Solids: Electron Conduction & Current

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Discussion Overview

The discussion revolves around the role of electrons in the conduction and valence bands of metals in relation to electrical current. Participants explore the contributions of partially filled valence bands and the conditions under which these electrons might contribute to conduction, focusing on metals and contrasting them with semiconductors.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants question whether electrons in the partially filled valence band can contribute to current, suggesting that they may have mobility but do not effectively conduct charge.
  • Others argue that in metals, the conduction band is either partially filled while the valence band is partially empty, or the two bands overlap, which complicates the understanding of charge transport.
  • One participant expresses confusion over terminology and asserts that the valence band of a metal does not play a role in charge transport properties, contrasting this with semiconductors.
  • Another participant mentions that in semi-metals like Bismuth and graphite, there can be a situation where one band is almost filled and another almost empty, suggesting a different perspective on band structure.
  • A participant proposes that conduction could occur through electrons in a partially filled valence band if the symmetry of their distribution is broken.
  • One participant challenges the idea that p-doped semiconductors would behave as insulators, implying that the discussion may overlook important distinctions between metals and semiconductors.

Areas of Agreement / Disagreement

Participants express differing views on the role of the valence band in metals and whether it contributes to conduction. There is no consensus on the interpretation of band structures or the implications for charge transport in metals versus semiconductors.

Contextual Notes

Participants reference specific band structures and terminology that may not be universally agreed upon, leading to potential misunderstandings. The discussion highlights the complexity of defining conduction mechanisms in different materials.

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Do electrons in conduction band are only responsible for current? Don't the electrons in partially filled valence band capable of moving contribute to current?
Material discussed-metals(conductors)
 
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Where is this partially-filled valence band in a metal?

Zz.
 
ZapperZ said:
Where is this partially-filled valence band in a metal?

Zz.
In metals either of the two cases exists-
1. Conduction band is partially filled and the valence band is partially empty. OR
2. Conduction and valence band overlap.
 
Quotes said:
In metals either of the two cases exists-
1. Conduction band is partially filled and the valence band is partially empty. OR
2. Conduction and valence band overlap.

Show me the band structure where the valence band is partially empty.

Zz.
 
ZapperZ said:
Show me the band structure where the valence band is partially empty.

Zz.
 

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This references are utterly confusing (what text are you using that has a typo of valence being replaced by "balanced"). The 2nd one, especially, is trying to differentiate between a metal and a semiconductor! We know about unfilled valence band for semiconductor. What I'm asking is for you to show me an example on the band structure of a metal that has a partially empty valence band.

I bet you that what is being described here is the difference between an insulating and a conducting state of a semiconductor! This is not a metal! A semiconductor may be conducting, but it is STILL not a metal! The valence band of a metal doesn't play a role in its charge transport properties. A semiconductor does!

I suggest you look very, VERY carefully at what you are reading and the terminology that you are using.

And please read this thread on why I consider the explanation of "band overlap" is flawed:

https://www.physicsforums.com/threads/how-does-band-structure-lead-to-metals-insulators.839172/

Zz.
 
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In semi-metals like Bismuth and graphite, you encounter the situation that there is one band almost filled and one band almost empty. Personally, I generally would avoid speaking of conduction and valence bands as this termini are clearly missleading.
 
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Quotes said:
Do electrons in conduction band are only responsible for current? Don't the electrons in partially filled valence band capable of moving contribute to current?
Material discussed-metals(conductors)
The electrons in valence band move with their corresponding group velocities but they don't conduct any charge because they move in different directions. I think it is possible to have conduction by the electrons in partially filled valence band provided that the symmetry of distribution in the band is broken.
 
If this were true, p-doped semiconductors would be isolators, too.
 

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