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One of the most important attribute of an exciton is its binding energy. This energy is calculated by subtracting the exciton energy from the difference in energy levels of the conduction and valence bands. The binding energy is NOT the same as the exciton energy. So the exciton is stable when its binding energy exceed zero. When Pauli blocking mechanism ...


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Z3 or Z1, Z2 excitons are labelled according to the locations of the peaks in the emission spectra of materials. These emission peaks are superimposed on the main band spectra linked to transitions between the conduction and valence bands. The occurrence of the various excitons can be attributed to the properties of the material system, such as the strength ...


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Disclaimer : I'm not sure that the following is the exact/complete answer to the question but maybe these elements could help. Equilibrium of a system under an external field Let say that you have an open macroscopic system $\Sigma$ (composed of identical particles) which is under the influence of an external time-independant but space-dependant ...


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A sum-frequency system with a "hot" mirror could act something like an optical switch: Unlike a switch, the output frequency will be different from either of the inputs. Edit: For an example of sum-frequency generation crystals see: Thorlabs Introduction To Periodically Poled Lithium Niobate (PPLN) (PDF) Thorlabs also sells hot mirrors.


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1) Your perturbation operator does not conserve the particle number of the phonons, so only even powers of it will contribute to equilibrium expectation values. Since you are interested only in the ground state, which doesn't have any phonons excited, this means that you have to create a phonon first. After that either another phonon can be created or the ...


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3-D bandstructures are still very useful. (2 dimensions for x and y and 3rd for Energy). For example, 3-D bandstructure plots allow us to see the Dirac cones that are found in the bandstructure of Graphene Note that the x and y direction cover every single point for a given z (which in this case is kz = 0). So in this sense this plot is more 'traditional' ...


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The answer probably lies in what are called Rayleigh–Bénard convection cells that often form hexagonal structures. Buoyancy, and hence gravity, is responsible for the appearance of convection cells. The initial movement is the upwelling of lesser density fluid from the heated bottom layer.[3] This upwelling spontaneously organizes into a regular ...


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There are 3 directions of vibration: namely the components $x$, $y$ and $z$ and each of these directions has 2 degrees of freedom; one of potential energy and one of kinetic energy. So in total there are $3\times 2 = 6$ degrees of freedom.


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Yes, the ions carry charge. However, the substrate is grounded so that current flows to keep the substrate neutral (and to measure the implanted dose). Otherwise a potential would rapidly build up (possibly up to the accelerating potential), changing the implant profile and/or causing arcing. (As an aside, this causes some difficulties when implanting or ...


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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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Kramers theorem is a very general result that in fermionic systems with time-reversal symmetry, energy levels are at least double degenerate. Circularly polarized light is an eigenstate of angular momentum. Angular momentum is odd under time reversal ($T$), since $\mathbf x\times\mathbf p$ is an angular momentum and $\mathbf p \mapsto -\mathbf p$ under $T$. ...


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I'm no expert, but Wikipedia has the answer you are looking for. Essentially, the charge is stored in a capacitor formed by a gate and the silicon. A voltage is put onto the gate, and an electric field will form in the silicon. Because of that electric field, charge carriers "generated" from the light hitting the silicon will drift into the field and stay ...


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With Bloch electrons, the Brillouin zone and all bands comprises a complete space. This means that while it is possible to write down and speak of states outside the Brillouin zone, these states are actually duplicates of the ones inside. In short, the Brillouin zone must be defined with a width in k-space of $2\pi/a$, with $a$ being the lattice constant. ...


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You are right that the Einstein model will break down if you are looking at low temperature. The next level of approximation, which does better, would be the Debye model. If you look in any intro. statistical physics book (I recommend Schroeder, Introduction to Thermal Physics if you are undergrad, or Kittel's Intro. to Solid State Physics) you will find a ...


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It is not affected at all. There is no net potential difference across the sandwich whether it is part of a circuit or not.



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