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Basically they are the same from a physics point of view, if you only look at crystalline materials. A semiconductor is defined to be insulating at $ 0 K $, while conducting at room temperature, although I don't recall, what level of conductivity is required to count as semiconductor. Technically, insulators are a more general group of materials, since they ...


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Earlier theoretical works have generally employed the classical approach where the exciton "hops" from one lattice site to another, the so called exciton hopping model. In more recent years, this model has been replaced by modern approaches based on the quantum coherence properties of the exciton. In the coherent propagation scheme, the exciton is modelled ...


3

The most truthful answer, to my mind, to this is simply "because it often works in practice." It is not obvious, a priori, that band structure should apply to any realistic solid. The Coulomb interaction is typically of the order of the Fermi energy. Nonetheless, thanks to the magic of Fermi liquid theory, this strong interaction somehow only results in ...


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Usually, when talking of the "band structure" of such a system one either refers to the non-interacting band structure (which relates to the free Green functions occuring in many methods to handle the interactions, like perturbation expansions or DMFT), or to the sharp features usually visible in the spectral function (which is more or less experimentally ...


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To change $v_F$ is to change the dispersion and density of states, which you generally expect to have an affect on every electronic and optoelectronic property. A particularly straightforward example: When you "gate" graphene (as you would a transistor), the fermi level moves, which you can measure most clearly by a cutting-off of IR absorption above a ...


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I'm not sure if I can help you on the part concerning the Weyl fermions. But your question seems to deal rather with what is a geometrical phase. Parallel transport and geometrical phase Maybe the more intuitive thing to do first is to draw a parallel between geometrical phase and parallel transport. As shown in the image of this wikipedia article, ...


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Careful! The essence of your question is a good thought but I think you are having several misconceptions. First of all, it doesn't make sense to talk about a phonon being directed towards a single atom. Phonons are delocalized. Secondly, the "input of temperature required to eject an electron" is a dangerous idea. You need to input energy to eject an ...



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