lesson 7 NEARLY FREE ELECTRON Solid State Physics

lesson #7: NEARLY FREE ELECTRON Solid State Physics M. Casalboni 2019/’ 20 An alternative way to look at the electron states and wavefunctions in a crystal is to start from electrons that are free to move from one atom to the others V Bravais points In a second time we switch on a weak potential and see what appen to the electronic states. 1/11

lesson #7: NEARLY FREE ELECTRON This means that we start to autostates with energies expressed by Solid State Physics M. Casalboni 2019/’ 20 2/11

lesson #7: NEARLY FREE ELECTRON This means that we start to autostates with energies expressed by Solid State Physics M. Casalboni 2019/’ 20 As we switch on the ion potential 3/11

lesson #7: NEARLY FREE ELECTRON What’s happening? Solid State Physics M. Casalboni 2019/’ 20 Not real «folding « rather SHIFT 4/11

lesson #7: NEARLY FREE ELECTRON Solid State Physics M. Casalboni 2019/’ 20 5/11

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lesson #7: NEARLY FREE ELECTRON Solid State Physics M. Casalboni 2019/’ 20 G Also hier but the matrix element 52 c is negligible!! 7/11

lesson #7: NEARLY FREE ELECTRON Solid State Physics M. Casalboni 2019/’ 20 Let us apply the time independent perturbation theory 8/11

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lesson #7: NEARLY FREE ELECTRON Solid State Physics M. Casalboni 2019/’ 20 11/11