The study of physical properties condensed phases of matter, including solids and liquids.

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52 views

Are there materials that strongly (macroscopically) vibrate under light of certain frequencies? If so why?

Picture an imperfect plane of loose particulate matter like sand or silt. Are there materials where if I shine light (not isotropically) on the plane I could get the particles to vibrate with large ...
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1answer
79 views

What is the difference between Fermi level and Fermi edge?

Just as in title: What is the difference between Fermi level and Fermi edge? My friend makes some research about XPS and he encountered this term. He knows what is Fermi level, but never heard about ...
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1answer
56 views

Is there any one lattice tight banding model (2D) hosts Dirac points as graphene does?

graphene has a two sublattice structure and it hosts two Dirac points. I wonder if there is some two dimensional lattice geometry which is simpler than honeycomb lattice, but also host Dirac points.
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0answers
47 views

Difference between a Hamiltonian and its mean-field form?

In most solid state physics text books, BCS theory is introduced in the following way: The authors introduce a mean-field parameter (based on the superconduncting pair) and upon that, they reduce the ...
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2answers
129 views

Dirac monopole of Berry curvature?

We know that there is an effective "magnetic field" in terms of Berry curvature, which leads to Luttinger's anomalous velocity, etc; and similarly there is also a "magnetic flux", which appears in ...
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49 views

Three-dimensional flat bands and how to create them?

Consider a three-dimensional non-interacting system with translational invariance. It is easy to create a two-dimensional flat band by putting this system into a uniform magnetic field. The energy ...
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0answers
50 views

Photon absorption and emission in 2nd quantization

I am looking for models which describe the interaction of matter (lets take a 1D chain of atoms) with photons, especially the emission and absorption. I would love to see the derivation of models in ...
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2answers
108 views

Why do Weyl points come in pairs in solid state system?

Quoted from "Beyond Band Insulators: Topology of Semi-metals and Interacting Phases" by Turner and Vishwanath: In 3D lattice models, Weyl points always come in pairs of opposite helicity; this ...
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0answers
30 views

Numerically evaluating momentum sums

For many-body systems, calculations often involve momentum sums, which are ultimately evaluated numerically for a finite system size $N$. The larger $N$ is, the more accurate the results. Is there ...
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59 views

Cooper Pair Breaking and Quasiparticle Excitations

My question concerns the breaking of Cooper pairs and the excitation of quasiparticles. At T = 0 all electrons are condensed in the ground state as cooper pairs. If one increases the temperature one ...
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0answers
73 views

Derivation of open boundary conditions for Non-Equilibrium Green's Function (NEGF)

It is widely claimed that the Non-Equilibrium Green's Function (NEGF) equations for the study of quantum transport have been derived from the many-body perturbation theory (MBPT). Yet the bridge ...
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47 views

Effect of doping in Superconductor

Doping an element (for example element substitution) could be lower down the critical temperature of superconductor, but i don't know the mechanism behind this, is it because more bosons need to ...
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0answers
38 views

Helium 3 atoms as fermions?

Helium atoms are composite particles so a priori their "single-particle" (in this case single atom) state is very complicated. They are nevertheless well-modeled by elementary fermions models like ...
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0answers
33 views

Twin and Detwin Crystals [closed]

Hello i would like to ask , what are twin and detwin monocrystals? what has to do with their crystalographic symmetry? any consequences ? any image also would be really helpfull! Thank you
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0answers
26 views

Rotational invariance of on-site repulsion term in Hubbard model

I'm trying to prove to myself something I assumed that was obvious: that the term $n_{\uparrow} n_{\downarrow} = \widetilde{n}_{\uparrow} \widetilde{n}_{\downarrow}$ where, $n_{\sigma} = ...
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1answer
64 views

Looking for a specific theory concerning Dark Matter [closed]

I am looking for the name of a theory positing that "empty" space itself is not empty, but has substance, and that "fabric" or "substance" is actually what we call Dark Matter. In theory, dark matter ...
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3answers
199 views

Difference between DMRG (density matrix renomalization group) and MPS (matrix product states)?

I am learning DMRG recently. I noticed there are many papers both in the DMRG approach and MPS (such as variational matrix product state (VMPS) by F.Verstraete and J.I.Cirac) approach. In my eyes, ...
2
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1answer
61 views

Particles, quasiparticles, and “stability”?

So I'm studying Fermi Liquid Theory, which concerns itself with quasiparticle excitations made by superpositions of single-electron wavefunctions. We create particle-like wavepackets which exist for ...
3
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1answer
193 views

Particle-Hole transformation in Superconductor

The Bogoliubov - de Gennes equation has a emergent particle-hole symmetry: $$ \mathcal{P}H\mathcal{P}^{\dagger} = -H\text{.} $$ My question is now what happen to the Nambu spinor: $$ ...
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0answers
150 views

Does Ashcroft and Mermin chapter 13 problem 4 have a misprint?

I've been working through Ashcroft and Mermin to review some aspects of solid state physics and I think problem 4 in chapter 13 might have a misprint. Since there don't seem to be errata available I ...
9
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1answer
128 views

Resources for algebraic topology in condensed matter physics

I wanted to know if anyone had any good introductions on algebraic topology for the theoretical physicist? I am particularly interested in applications to condensed matter physics, but would be happy ...
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2answers
175 views

Why do metals become insulators when oxidized?

I don't know the connection between how forming a new bond with oxygen then changes the density of states to transform the metal into an insulator. It seems like a very powerful transformation.
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0answers
39 views

Fermi Golden Rule derivation of quasi-electron lifetime

I wonder if there is a detailed derivation of the quasi-electron lifetime: \begin{equation} \frac{1}{\tau_k}=\frac{2\pi}{\hbar}\frac{1}{V^2}\sum_{k', ...
2
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1answer
68 views

How do we know that the x-ray pattern is in the reciprocal space? [closed]

I wonder if any one can tell that why do we consider the x-ray pattern (for example, a x-ray pattern on a film for a crystal) in the reciprocal space? (I don't want any explanation about the Ewald ...
2
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1answer
37 views

How deep within the sample can the DOS(density of states) be detected by STM(scanning tunnel microscope)?

Using STM equipment, we can get the LDOS(local density of states) on the surface of a sample. I want to know whether the LDOS within the sample(not surface) can be detected by STM. what is the ...
6
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2answers
171 views

Is the thermal conductivity of metals affected by magnetic fields?

Especially for a ferromagnet a magnetic field should have a field-induced band shift in the density of states but I wonder if this shift is big enough to be significant and affect the thermal ...
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0answers
11 views

Is it posssible to numerically simulate a metal layer the same way as a semiconductor one

I need to simulate a schottky junction device. Unfortunately, the software for simulation (AFORS-HET) doesn't allow adding metal (I need to simulate aluminum contact) layers (but it allows to add ...
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0answers
39 views

Is the saturation magnetization of a thin film different if you apply the field at different directions?

I'm getting different values of the saturation magnetization when I measure them in-plane versus out of plane. The saturation magnetization for the out of plane measurement is greater than in the in ...
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0answers
24 views

Choosing a basis state for density functional theory calculations

How do we choose basis set of wave functions for expanding the eigenfunctions of the kohn-sham equations? I mean given a material,what should i look for in order to choose my basis functions?
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1answer
39 views

Why is the vapor pressure important for people that grow films in high vacuum chambers?

I don't understand what this vapor pressure is. The definition from wikipedia is unclear to me. If I look at two materials and one has a higher vapor pressure than the other, does that mean that the ...
2
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1answer
162 views

What is the significance of the Debye temperature from a materials perspctive?

If I look at a table of different metals and their Debye temperatures, what does the variation in these temperatures tell me about these materials?
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0answers
98 views

Wen plaquette model with one kind of plaquette operator

Let us say that we modify the familiar Wen plaquette model so that only one kind of plaquette operator is in the Hamiltonian which is a product of $\sigma_z$s, what kind of topological order or state ...
3
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2answers
62 views

How to measure transverse current-current correlation at arbitrary wave vector and frequency

Let $\hat J^{\mu}(t,\boldsymbol r) \equiv (c \hat \rho(t,\boldsymbol r), \hat{\boldsymbol J}(t,\boldsymbol r))$ be the density-current operator at spacetime coordinate $(t,\boldsymbol r)$, in the ...
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0answers
60 views

electron phonon interaction

I am reading the paper on deriving electron phonon interaction hamiltonian by Frohlic.http://rspa.royalsocietypublishing.org/content/royprsa/215/1122/291.full.pdf Here author has introduced the ...
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2answers
95 views

What are the conditions to observe gapless modes at the boundary for 1D case?

We observe gapless modes at the boundary for the case of SSH model or Polyacetylene The Hamiltonian for SSH model has particle hole and time reversal symmetries, it also has a Dirac like spectrum. It ...
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0answers
140 views

How do you fourier transform a tight binding hamiltonian numerically?

The task is to do a fourier transformation of a tight binding hamiltonian of a 1D-chain with unit cell size 2, but even after many tries and googling I still don't have a idea how to do it correctly. ...
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1answer
58 views

Elementary introduction to (quantum) hall effect

Where can I find an elementary introduction to classical and quantum hall effect? Only physics I know is some basic quantum mechanics, EM and statistical physics. My goal eventually is to understand ...
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1answer
330 views

Why does chalk dust stick to a chalkboard?

I understand that friction causes the chaos dust to come off the stick of chalk, but what exactly is causing the chalk dust to stay on the chalk board until rubbed off?
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4answers
460 views

Are fermions intrinsically non-local?

Background: When one studies quantum mechanics of more than one particle, one learns that all fundamental particles can be classified as either bosonic or fermionic. Fermions have a spinor structure, ...
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0answers
35 views

If I know how many atoms I have in a film, can I know the total magnetic moment?

Say I have a Co film and I know its volume so I know the total number of atoms in it. Using this plus the knowledge that each atom has a magnetic moment of 1.7 Bohr magnetons, would the total magnetic ...
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1answer
95 views

Is surface plasmon Fermion or Boson?

When photons are converted into surface plasmon in some artificially designed structure such as metal gratings to provide the additional momentum, is the boson character of photons are preserved or ...
2
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2answers
105 views

Exact Diagonalization of a BdG Hamiltonian on a Finite Lattice

I would like to numerically find the edge modes of a $p_x$ + $i p_y$ BdG Hamiltonian. The lattice version is given by H = $\sum\left[-t \left(c_{m+1,n}^{\dagger} c_{m,n} + \text{h.c} \right) - ...
5
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0answers
77 views

How to perform stroboscopic measurements for Floquet topological insulators?

Floquet topological insulators (arXiv:1008.1792, arXiv:1211.5623) have attracted much research interests in condensed matter physics. The goal is to realize topological insulators from trivial ...
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1answer
44 views

Fermi Surfaces meeting

I know the fermi level is the highest energy level in an atom for its electrons and the fermi surface is (in reciprocal space) a sphere of radius fermi level, if that makes sense. So when two ...
3
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1answer
161 views

Mean field approach to toric code

Toric code is one of the few exactly solvable model in condensed matter, however, like the paper (http://arxiv.org/abs/1104.5485) that uses SU(2) slave fermion to "solve" Kitaev's honeycomb model, is ...
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0answers
89 views

Particle Hole Transformation of Hamiltonian

The particle hole transformation for a bipartite lattice $\Lambda$ (with sublattices $A$ and $B$) can be written as $$U^\dagger c_{i,\uparrow} U = \epsilon(i) c^\dagger_{i\uparrow} \\ U^\dagger ...
0
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1answer
91 views

What is the importance of the biquadratic interaction in the AKLT model?

The AKLT in a spin-1 Heisenberg chain can be realized when we introduce the bi-quadratic exchange interaction in addition to the bi-linear interaction. I would like understand this interaction more ...
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46 views

Question(s) Regarding the Lindhard Function

As a theoretical chemist, I'm slightly outside of my element on a project my advisor gave me, so I come to your for help and direction. Basically, he wants me to integrate the imaginary part of the ...
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0answers
53 views

Proof of periodicity of Floquet Green's function

It is claimed in many papers that the two-time Green's function in time periodic Hamiltonian case is periodic in the average time, i.e. \begin{equation} G(t+T,t'+T)=G(t,t') \end{equation} when ...
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1answer
47 views

electron shell jumping in Iron?

I understand a "little" about electron shell jumping, I was wondering about "Iron", If iron was heated to a gas, perhaps held in a vacuum maybe even under pressure, would the added energy make the ...