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New answers tagged condensed-matter

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In fact, the assumption of a uniform density neutralizing background is called the free electron model and is one of the first steps we take in the analysis of electronic properties of solids. Unfortunately, while the model makes multiple successful predictions (e.g., the Wiedemann-Franz law at high temperature), experimental evidence such as the temperature ...

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There is no resistance is this scenario. You need a scattering mechanism like electron-phonon scattering or electron-defect scattering to obtain a non-infinite conductivity.

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I would disagree here. The coherence length is the length scale where the electrons stay in their coherent, superconducting state. This gets important on boundaries of a superconductor (i.e. the proximity effect) or at vortices of a type II superconductor in the mixed phase. In both examples, you can measure the coherence length. This is done by fitting the ...

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As 'quasi particles' those newly discovered weyl fermions only exist as specific wave points in a specific material. In that sense, you would not get a 'shocked' as humans are made of 'weyl-fermion-insulated material'

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$\renewcommand{ket}[1]{|#1\rangle}$ The basic logical connection here is $$\text{symmetry} \rightarrow \text{degeneracy} \rightarrow \text{avoided crossing} \rightarrow \text{band gap} \, .$$ $\textrm{symmetry}\rightarrow \textrm{degeneracy}$ Consider an operator $S$ and let $T(t) = \exp[-i H t / \hbar]$ be the time evolution operator. If  [ T(t), S] = 0 ...

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There is a sense in which a massive fermion can be thought of as made up from two Weyl fermions of opposite chirality. While I haven't read the paper in question (it's behind a paywall) I get the impression that the quasi-particle detected in these experiments results from electrons behaving as if they were a pair of Weyl fermions, and that the result could ...

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If there is only one band maximum in the BZ, this point is one of the high-symmetry points of the BZ. However, there can be cases where there are many points which are a band maximum and they are not at one of the high-symmetry points of the BZ. These points however are all connected by a symmetry operation. An example of a system with band minima away ...

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I'll comment on the second issue that $E_F$ should always be greater than zero, which leads to a finite scattering rate. However, that's beside the point because in an ideal Fermi liquid at $T\rightarrow 0, |E_F-E|\rightarrow0$, the scattering rate becomes zero, which leads to an infinite lifetime. If in graphene, as you say, the independent particle picture ...

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This is interesting! Just want to ask a few questions for clarification: (1) Which geometry did you use for the states? disk, sphere, torus? (2) Which set of Slater determinants did you computed overlaps with? for example, did you use a fixed single particle basis and did the optimization over occupation numbers only, or did you allow for changes of the ...

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The entanglement of any region in a matrix product state of bond dimension $D$ is bounded by $S\le 2\log D$. Thus, in order to simulate a system with a lot of entanglement, the bond dimension (and thus the memory and time of the computation) will grow exponentially with the entropy. Conversely, we know that if for a state $\vert\psi\rangle$ the ...

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This photo from a proposal for stainless steel stents ( to be used in humans) is enlightening stainless steel scanning electron microscope (SEM) photo The crystallization is obviously random, with a lot of pores at that size ( which is what they try to increase for the purposes of the study). This means that the facets of the crystals are not on a ...

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LO-TO splitting is caused by the long-ranged nature of the Coulomb interaction (i.e. because the Fourier Transform of the Coulomb interaction,$4\pi e^2/q^2$, is not well-defined at $q=0$). Also, it occurs near the Brillouin zone center, but not at the exact Brillouin zone center because of retardation effects (i.e. the finite speed of light). At $q=0$, the ...

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I think OP's question is about the p-h symmetry in BdG equation of superconductivity. This is really an exact p-h symmetry (in mathematics), but it is however a redundancy of description. Since it doubles the degree of freedom.

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