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Thermodynamic relation $N=-\frac{\partial J}{\partial \mu}$ exactly gives you the particle number equation, wherein $J$ is the macroscopic thermodynamic potential, i.e., the quantity $F$ in your quest …

For a Weyl semimetal with a pair of Weyl points along $z$ axis, let's consider a slab geometry that is only finite in, say, $x$ direction (infinite in $y,z$). Will the surface state still be gapless? …

Has the technique of both spin- and time-resolved angle-resolved photoemission spectroscopy (ARPES) been realized and applied anywhere?

I'd like to study an inhomogeneous system, i.e., momentum is not a good quantum number therein. Therefore, I tried to calculate temperature Green functions like $\mathcal{G}(x_1,x_2;\tau)$, or its two …

There is a table of Matsubara frequency summations on Wikipedia. The 8th one, $$\frac{1}{\beta}\sum_{i\omega}\frac{(i\omega)^2}{(i\omega)^2-\xi^2}=-\frac{\xi}{2}(1+2\eta n_\eta(\xi))$$ with $\eta=\pm1 …

The question is about collective modes of charge density waves, i.e., amplitude and phase fluctuations $\delta,\phi$ of the order parameter $\Delta(x,t)=(\Delta_0+\delta)e^{i\phi}$. I read on p.1 of …

In some topological materials, e.g., the quantum (anomalous) Hall state and some related variants, the Hall conductivity $\sigma_{xy}$ is quantized and directly related to the Chern number, which corr …

There are models of the 3D Dirac semimetal. For example, proposed in this paper, when $k_\pm=k_x\pm ik_y$ and $M=m-|\vec{k}|^2$, $$H=\begin{bmatrix} M & k_+ & 0 & 0 \\ k_- & -M & 0 & 0 \\ 0 & 0 & M & …

The Kohn anomaly is the singular behavior of phonon softening in materials, for which a mean-field theory is the BCS type and is usually described to be driven by lowering the temperature till some de …

The bottom line is the spontaneous symmetry breakdown from global $U(1)$ to $\mathbb{Z}_2$ and the concomitant rigidity of the omnipresent coherent phase down to which the system breaks. However, both …

I found in a paper the following explanation. Unfortunately, I can't understand it. Can anyone help me on this? In the limit of equal spins an optical magnon with k=0 gets an acoustical one at the …

Can anyone shed light on the comparison between these two concepts?

It is well known that we have got many kinds of quantized macro(meso)scopic harmonic oscillators or so in tiny mechanical systems. People are talking about cavity cooling and so on. However, it is si …

Consider a free electron system, say, a tight-binding lattice model. Does its DC longitudinal conductivity from the Kubo formula always diverge/vanish theoretically? Since there is not any scattering/ …

Given a Matsubara Green function $\mathscr{G}(i\omega)$, analytic continuation $i\omega \mapsto \omega+i0^+$ leads to the retarded/advanced Green functions $g^{r(a)}$. There is also an ansatz in equil …