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Band Theory, Kittel chapter 7

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Kronig-Penney model<br />

for 0 < x < b<br />

ψ ( x) = cos( kx), ψ ( x)<br />

=<br />

1 1 2<br />

for b < x < a<br />

sin( kx<br />

1<br />

)<br />

k<br />

1<br />

k<br />

=<br />

2 mE ( −V1<br />

)<br />

<br />

1 2<br />

ψ<br />

ψ<br />

x k x b kb<br />

k sin( k ( x−b))sin( kb)<br />

1 2 1<br />

1() = cos(<br />

2( − ))cos(<br />

1<br />

) −<br />

,<br />

k2<br />

cos( k ( x−b))sin( kb) sin( k ( x−b))cos( kb)<br />

2 1 2 1<br />

2() x = +<br />

.<br />

k1 k2<br />

k<br />

=<br />

2 mE ( −V2<br />

)<br />

<br />

2 2<br />

Except for the coefficients, these are the same solutions as we found for light<br />

in a layered material.

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