Are There Any Cases of Non-Constant Particle Mass in Solid State Theory?

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Discussion Overview

The discussion centers on the concept of particle mass within solid state theory, specifically addressing the notion of non-constant particle mass and its implications for electrons and holes in semiconductors. The scope includes theoretical considerations and the behavior of quasi-particles in solid state physics.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant references a note in a book suggesting that mass is generally assumed constant in certain structures, questioning if non-constant mass cases exist.
  • Another participant introduces the concept of "effective mass" for quasi-particles like electrons and holes, indicating that this mass can vary with changes in band structure.
  • A subsequent reply distinguishes between real electrons and quasi-electrons, asserting that while effective mass may vary, the intrinsic mass of an electron remains constant.
  • It is noted that solid state theory typically operates under the assumption that the electrons discussed are quasi-electrons, implying a common acceptance of this framework.

Areas of Agreement / Disagreement

Participants express differing views on the nature of particle mass, particularly regarding the distinction between real and quasi-particles. There is no consensus on the existence of non-constant mass cases beyond the context of effective mass in quasi-particles.

Contextual Notes

The discussion highlights the dependence on definitions of mass in different contexts, particularly the distinction between effective mass and intrinsic mass, which may lead to ambiguity in understanding particle behavior in solid state theory.

TriKri
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In the book "The Physics of Semiconductors" by Marius Grundmann, there is a note on one of the pages, saying:
Generally, \Psi'/m should be continuous, however, in the present example the mass is assumed constant throughout the structure.

I have never heard of a case where a particle would have a non-constant mass, is there any such case at all?
 
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Electrons and holes in semiconductors are quasi-particles. They have an "effective mass" which is given in terms of the second derivative of the band dispersion. This mass can vary if the band structure varies.
 
In that case it would be more like a quasi-electron, not a real electron, right? Because the electron itself still has a constant mass.
 
In Solid state theory, you take it usually for granted that the electrons you are talking about are quasi-electrons in reality.
 

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