Recent content by csmallw

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    In an infinite quantum well, why Δn=0?

    Thanks, this ought to help.
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    In an infinite quantum well, why Δn=0?

    Ah! My reference text misled me. It seems to be the case that Δn = 0 must hold even for the finite square well. Consider two bound states |1> and |2>, with distinct energies E1 and E2, and consider the matrix element, \langle 1 | H | 2\rangle. H can operate to either the left or the right...
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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?

    Thanks to you both. These comments are helpful.
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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 mostly been looking at Ascroft & Mermin, pp. 225-229, but also Ziman (Principles of the Theory of Solids), pp. 184-186. There's a bit too much material to quote, but after closer inspection, I guess Ashcroft and Mermin make no statements about the sign of the energy of holes, though their...
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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?

    Thanks! Both these responses were helpful.
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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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    Brillouin Zone Confusion

    Not exactly. The volume of the BZ divided by the volume of a k-state is equal to the total number of available k-states for a given band in the system, i.e., the number of slots in the band that are available for charge carriers (electrons) to inhabit. Thus, if the volume enclosed by the Fermi...
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    Can one electron decay into an electron plus a phonon?

    Great! I am declaring my original post to be entirely correct. Thanks for everyone’s comments. This statement that the diagram is incomplete is not right, as far as I can tell. It would only be accurate for the example with electrons and photons in a vacuum, and the reason is that the diagram...
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    Can one electron decay into an electron plus a phonon?

    Thanks, and yes, the typical electron-phonon interaction is exactly what I am trying to describe. I am interested to know if Feynman diagrams would be an appropriate way to describe the electron-phonon interaction in a "cartoon" fashion. If so, what do the lowest-order diagrams look like?
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    Can one electron decay into an electron plus a phonon?

    Can you elaborate on what you mean when you say that the Feynman diagram is incomplete? Nomenclature aside, what I am trying to ask is, in a metal or semiconductor, can one electron in a state at energy \omega spontaneously scatter into one electron at a lower energy state \omega-\Omega, plus...
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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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    D-wave superconductivity: Functional forms?

    Thanks. Funny you should mention writing your thesis...I'm getting ready to do that myself in a month or two, which is why I am interested in getting a better handle on these concepts ;)
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