Discussion Overview
The discussion revolves around the role of phonons in momentum conservation during indirect electronic transitions in crystals. Participants explore the relationship between phonons, crystal momentum, and the momentum of electrons and the lattice, focusing on theoretical implications and conceptual clarifications.
Discussion Character
- Technical explanation
- Conceptual clarification
- Debate/contested
Main Points Raised
- Some participants assert that phonons do not carry momentum but instead carry crystal momentum, which they argue are distinct concepts.
- One participant suggests that in an indirect transition, the change in crystal momentum of the electron is compensated by a change in the crystal momentum of the phonon.
- Another participant emphasizes that the true momentum of the electron is not relevant in this context, as it is not in a momentum eigenstate.
- There is a discussion about the mean value of the true momentum of the electron, defined as the mass of the electron times its group velocity.
- A participant mentions that the lattice can absorb arbitrary amounts of momentum, implying that momentum conservation is straightforward in this context.
Areas of Agreement / Disagreement
Participants express differing views on the nature of momentum and crystal momentum, with no consensus reached on the implications of phonons in momentum conservation. The discussion remains unresolved regarding the separation of phonon momentum from crystal momentum.
Contextual Notes
Participants reference the distinction between true momentum and crystal momentum without fully resolving the implications of these definitions. There are assumptions about the behavior of electrons in non-momentum eigenstates that are not explicitly detailed.