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

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11
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1answer
793 views

When can we take the Brillouin zone to be a sphere?

When reading some literatures on topological insulators, I've seen authors taking Brillouin zone(BZ) to be a sphere sometimes, especially when it comes to strong topological insulators. Also I've seen ...
1
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1answer
92 views

What makes a system topological?

As I understand, if the Chern number which is obtained by integrating Berry curvature over a surface with a boundary is an integer, then the Chern number is a topological invariant. So when does Chern ...
2
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0answers
45 views

Relation between Berry phase and degeneracies, the example of Hall effect in graphene

In principle, the Berry-curvature can be related to the degeneracy of some underlying energy levels, using the adiabatic picture and expanding the Berry's expression in the language of instantaneous ...
1
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0answers
279 views
4
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2answers
240 views

How to derive the Aharonov-Bohm effect result?

In the derivations of the Aharonov-Bohm phase, it is directly mentioned that due to the introduction of the vector potential $A$, an extra phase is introduced into the wavefunction for case $A\neq0$ ...
1
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1answer
86 views

How can a torus admit half a flux quantum, and why does a vortex induce an AB phase?

There is an issue that I have with the argument given in “Topological Degeneracy of non-Abelian States for Dummies” http://arxiv.org/abs/cond-mat/0607743 , regarding the ground state degeneracy of the ...
0
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0answers
21 views

Hydraulic conductivity and flow rate

I have several sources that have the following equation relating the change of volume in a cell to the hydraulic conductivity (permeability coefficient) $L$ and pressure differential $\Delta P$: $$ ...
8
votes
1answer
511 views

Do EM waves transmit spin polarization?

Suppose you have a normal dipole antennae (transmitter and receiver) . Spin polarized current (as opposed to normal current) is sent into the transmitter, it emits an EM wave and the Receiver receives ...
1
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1answer
31 views

Understanding FCC and BCC Bravais Lattices

A book I am reading states that one possible definition of a Bravais Lattice is that the surroundings will look the same from whichever lattice point you observe from. Consider for example the simple ...
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0answers
21 views

Advanced methods of theoretical condensed matter [duplicate]

I am looking for an online course devoted to the advanced methods of theoretical condensed matter physics. It is good if the course offers free materials like lectures, homework assignments etc. ...
1
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0answers
27 views

Magnus Expansion in Floquet theory

I wonder how to obtain the second equality as follows in Eq. (44) of http://www.tandfonline.com/doi/abs/10.1080/00018732.2015.1055918?journalCode=tadp20 \begin{eqnarray} ...
2
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0answers
29 views

How do we determine whether the tight binding model is valid for a material?

Right now I know that the tight binding model applies when electrons are tightly localized around the ions in the material. How do we determine whether the electrons are actually tightly localized for ...
4
votes
1answer
86 views

Why does a Heisenberg magnet break the O(3) symmetry in stead of SU(2)?

As stated in the question, why does a Heisenberg magnet break the $O(3)$ symmetry while degrees of freedom of the underlying spins are $SU(2)$?
10
votes
2answers
583 views

Nambu-Goldstone bosons from a quantum anomaly symmetry breaking?

We know that: Nambu-Goldstone bosons come from Goldstone theorem: a spontaneous (continuous)-symmetry breaking of the system leads to massless scalar modes. quantum anomaly: is the anomalous ...
7
votes
1answer
3k views

Which derivation of drift velocity is correct?

In the derivation of drift velocity I have seen two variations and want to know which one's correct. $s=ut+\frac{at^2}{2}$ Assume that the drift velocity of any electron in any conductor is : ...
4
votes
1answer
104 views

What is the difference between superfluidity and Bose condensation?

My question is about zero-temperature ground state of a Bose system. Suppose that the system stabilizes a BEC order parameter, say $\langle b^+ \rangle$, and fixes its phase. Is this a superfluid? And ...
4
votes
1answer
63 views

Density of states in a system of interacting electrons

When we are introduced to the density of states in typical band-theory problems we neglect interaction between electrons, and thus we define the density of states of a sigle particle as: ...
0
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0answers
14 views

variable range hopping

Having an Arrhenius plot for the logarigthm of conductivity vs 1000/T, I noticed a region in which i assume variable range hopping takes place. Then i draw the plot logarigthm of conductivity vs ...
0
votes
1answer
37 views

Review article recommendation in the field of 2d materials

I am new to 2d materials. I tried to search related review articles in review of modern physics, but did not find anyone covering the whole of the 2d material area. Anybody can recommend some latest ...
3
votes
1answer
89 views

Benefit of using Matsubara Green function

Physicists often calculate Matsubara Green function and then perform an analytic continuation $i\omega_n \rightarrow \omega +i\eta$ to obtain the retarded Green function. Why is doing so better than ...
-1
votes
1answer
72 views

What is the correct statement of Kirchhoff's Law of Thermal Emission?

There are various quite different statements in textbooks and other science literature as to Kirchhoff's Law of Thermal Emission. So, what is the correct statement of Kirchhoff's Law of Thermal ...
6
votes
1answer
242 views

Why is $\textbf{D}$ the response to $\textbf{E}$?

In the text Wooten, equation 2.69 shows $\textbf{D}$ being the response to $\textbf{E}$ with $\epsilon$ as the response function: $$ \textbf{D}(\textbf{r},t) = \int d\textbf{r}^{\prime} \int ...
0
votes
0answers
12 views

What is the best book for understanding solid state physics for undergraduates? [duplicate]

I have read Charles Kittel's book. But I thought it is higher than undergraduate level. Can any body suggest a best book which explains from the beginning of the topic?
2
votes
1answer
47 views

What is the Goldstone mode when rotation symmetry breaks in lattice?

In textbooks for introducing Goldstone mode, people usually consider about phonon as a Goldstone mode emerging from translation symmetry breaking in lattice. However, the rotation symmetry also ...
1
vote
1answer
121 views

Density of states for graphene

I have seen a lot of plots for the density of states for graphene: but have been unable to find the calculation explicetely. I know the dispersion relation for graphene is $E_{\pm} (\textbf{k}) ...
1
vote
1answer
48 views

what does d spacing between planes in a crystal lattice mean?

I have trouble understanding the meaning of d-spacing. d spacing is supposed to give the interplanar distance. for a cubic lattice $$d_{hk \ell}= \frac {a} { \sqrt{h^2 + k^2 + \ell ^2} } $$ What i ...
3
votes
1answer
259 views

Hartree-Fock correction to $e$-$e$ interaction

The corrections to the energy per electron in a jellium model (uniform distribution of positive ion charge approximation to the regulated long range order ionic array) is given by (in units of Ry) ...
0
votes
1answer
46 views

partition function of the U=0 Hubbard model

I'm trying to derive the following partition function for the U=0 Hubbard model: $Z=\prod_\mathbf{k}(1+e^{-\beta(\epsilon_\mathbf{k}-\mu)})$ My try was to use: $Z=\sum_{\sigma,\mathbf{k}} ...
0
votes
1answer
80 views

General properties of Matsubara frequency summations

By properties such as linearity, shifting, commutativity, etc. I was hoping to evaluate something like, $$S_\eta = \dfrac{1}{\beta}\displaystyle\sum_{i\omega} ...
2
votes
2answers
61 views

Fetter & Walecka's derivation of second quantised potential term in many-particle TDSE

For the potential term in the Hamiltonian, I understand that we go through the same process as with the kinetic energy term. On the RHS of the TDSE, we get something like ...
3
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0answers
131 views
-7
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2answers
236 views

Is Planck’s proof of Kirchhoff’s Law of Thermal Emission false; and if it is not false why is it not false? [closed]

In his book ‘The Theory of Heat Radiation’, Max Planck adduced his theoretical proof of Kirchhoff’s Law of Thermal Emission. However, there are some problems with that approach, some of which we ...
2
votes
1answer
40 views

Calculate the laser heating on a crystal

Let's say I'm doing an optical experiment. I focus a laser on a crystal with a certain amount of power. The crystal's temperature is regulated to a certain temperature but it is localy heated by the ...
1
vote
1answer
39 views

Why does a dynamical gauge field accompany fractionalisation?

I'm trying to understand fractionalisation, of which spin-charge separation is an example. I've read that this is accomplished by introducing a Lagrange multiplier field, which becomes a dynamical ...
13
votes
1answer
742 views

How does Haldane conjecture follow from the topological $\Theta$ term

The one dimensional SU(2) Heisenberg quantum spin chain is known to be described by the 1+1d O(3) nonlinear $\sigma$ model with a $\Theta$ term, following the action ...
4
votes
0answers
54 views

In what circumstances, can exchange interaction acquire temperature dependence?

Heisenberg exchange interaction (sometimes called as magnetic stiffness?), originating from the Coulomb interaction and the Fermion statistics, is widely used in theories of magnetism. Conventionally, ...
1
vote
1answer
35 views

Can the probability of electron capture in a metal hydride be increased by extreme electric current?

An example of a metal that can hold a lot of hydrogen is palladium. The hydrogen atoms (protons) in the metal lattice are positive and the electrons are negative. When a large electric potential is ...
3
votes
1answer
243 views

Why is the projective symmetry group (PSG) called projective?

As discussed by Prof.Wen in the context of the quantum orders of spin liquids, PSG is defined as all the transformations that leave the mean-field ansatz invariant, IGG is the so-called invariant ...
4
votes
1answer
88 views

Self-energy of a Fermi liquid

A weakly correlated many-electron system can be viewed in a first approximation as a Fermi liquid, meaning that it behaves similarly to a non-interacting electron gas with renormalized parameters. In ...
3
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0answers
35 views

Weyl semi metal vs entanglement entropy

In 2+1D, entanglement entropy (EE) is crucial for identifying a topological phase. What happens in 3+1d case? e.g. what are the behaviours of EE in WSM and trivial states?
1
vote
2answers
68 views

Why is amorphous classified solid?

Because it does not have a crystal structure, it is hard to find physical similarities with a solid. Why isn't it then another state other than solid? The physics of amorphous is also quite different ...
4
votes
1answer
31 views

What's the difference in the film between sputtering deposition and an ebeam evaporator?

I know the differences between the two deposition techniques, but what about the difference in the properties of the resulting films? All things being equal (such as substrate temperature), would ...
2
votes
2answers
67 views

Variant of the Sokhotski–Plemelj theorem

I am aware of the Sokhotski–Plemelj theorem (I have also heard people referring to it as the "Dirac identity") which states that in the limit $\eta\rightarrow 0^+$ $$\frac{1}{x\pm i\eta}=\mathcal ...
2
votes
1answer
128 views

Topological invariant for interacting systems using single particle green functions?

Why Single particle green's function is (preferred) used to find topological for interacting systems? $N_1 =\frac{\epsilon_{ijk}}{24 \Pi ^2} \int dw d^3k G \partial_i ...
4
votes
2answers
335 views

Is there any relation between temperature dependence of resistance and fermi energy in metals?

Given that the resistance varies linearly with temperature in metals, is there any way we can calculate the Fermi energy from this information?
3
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0answers
70 views

What are fragmented condensates?

It is defined that if more than one eigenvalue of the one-body density matrix are macroscopically occupied the condensate is said to be fragmented. $$ n^{(1)},n^{(2)},...=\mathcal{O}(\mathcal{N}) $$ ...
3
votes
1answer
156 views

Looking for a good introductory-level review of pseudopotential methods

I'm looking for a good introductory-level review of pseudopotential methods. In particular, I'd like to understand how the self-consistent pseudopotential methods work.
0
votes
0answers
63 views

Fetter & Walecka's derivation of second quantised canonical Schrodinger equation for fermions

On page 18, before the occupation number variables for states i and j are changed $n_i \rightarrow n'_i = n_i - 1$ and $n_j \rightarrow n'_j = n_j + 1$ respectively, could we not have rewritten eq. ...
1
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0answers
22 views

How well can ADSCFT related approaches to condense matter predict measurable properties of materials? [closed]

Are ADSCFT techniques able to make any predictions about measurable properties of any materials? Are there some interesting but somewhat accessible looking problems left in this area to solve or is ...
2
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0answers
21 views

Non-equilibrium electronic distribution in the time-relaxation approximation - Which is the boundary condition?

In Chapter 13 of Ashcroft-Mermin - "Solid State Physics", the following non equilibrium electronic phase-space distribution for the semiclassical electrons in a periodic crystal is derived: ...