Difference between phonon and electron excitation

[rwooduk]

Homework Statement

Homework Equations

Debye approximation.

The Attempt at a Solution

For the first question (a) he has taken the lowest energy transition to be 0.2eV. (3eV-2.8eV with k=0)
For the second question (b) he has taken the lowest energy transition to be at k=1. (it works out as 0.15eV)

I understand why it's taken at k=1 for the electron but why is the lowest energy transition taken at k=0 for the first question?

Thanks for any help clearing this up.

 

[mark726]

Hello,

Thank you for your question. The reason why the lowest energy transition is taken at k=0 for the first question is because in the Debye approximation, the lowest energy transition is assumed to occur at the Brillouin zone center (k=0). This is because at the Brillouin zone center, the energy levels are more closely spaced and therefore transitions between these levels require less energy.

In the case of the second question, the electron is in a different energy state and therefore the lowest energy transition occurs at a different k value. This is because the electron has a different energy level structure and therefore transitions between these levels require different amounts of energy.

I hope this helps to clarify the reasoning behind taking the lowest energy transition at k=0 for the first question. If you have any further questions, please don't hesitate to ask.Scientist