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    In an infinite quantum well, why Δn=0?

    I've been reading up a bit on semiconductor quantum wells, and came across a selection rule for an infinite quantum well that says that "Δn = n' - n = 0", where n' is the quantum well index of an excited electron state in the conduction band, and n is the index of the valence band state where...
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    What defines a polaron?

    Is there an easy-to-articulate difference between a polaron and an electron exhibiting electron-phonon coupling? Until yesterday, I had been under the impression that the difference between the two phenomena was related to the strength of the coupling. However, I looked up "polaron" on...
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    What is the momentum of a hole in a semiconductor?

    I've been playing around with some ideas of electron-hole pairs in semiconductors lately, have realized that I'm confused about some basic conventions that maybe the physics forum community could help clear up. Let's imagine that we have a direct gap semiconductor initially at zero temperature...
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    Who is this "Kallen" and what does he represent, anyway?

    Hi all, I'm working on a Green function chapter of my dissertation, am referencing the equation, G(k,\omega) = \int_{-\infty}^\infty \frac{A(k,\omega')d\omega'}{\omega - \omega' + i0^+}, and I am trying to figure out the best way to credit it. I have noticed that condensed matter texts...
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    Can one electron decay into an electron plus a phonon?

    In a metal, can one electron decay into one lower-energy electron plus one phonon? (i.e., can the attached Feynman diagram occur?) If we replace phonons by photons and consider the process in a vacuum, I guess this is prohibited because you can always boost to a frame where the incoming and...
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    Is there a conservation law associated with C4 symmetry?

    I know--because of Noether's theorem--that continuous rotational symmetry implies conservation of angular momentum, and that continuous translational symmetry implies conservation of linear momentum. It also turns out that the discrete translational symmetry exhibited by a Bravais lattice...
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    Analytic Approximation for an Oscillatory Integral

    I'm looking for a way to write down an analytic approximation for the following integral: \int_0^\infty \frac{k \sin(kr)}{\sqrt{1+v^2(k-k_F)^2}}dk Let's assume that v kF >> 1, so that the the oscillating piece at large k doesn't contribute much uncertainty. Ideas? Thus far, Mathematica has...
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    D-wave superconductivity: Functional forms?

    Two questions, really: I’m finding it hard to wrap my head around the connections between k-space and real-space for d-wave symmetry, as well as the connections between “order parameter,” “gap,” “Cooper pair wave function,” and “superconducting wavefunction,” which are all mentioned at various...
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