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

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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 ...
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1answer
112 views

Simplest Live Demonstration of Adiabatic Transport

I have to give a presentation on Berry phase. I would like to give the simplest live demonstration of adiabatic transport. If I move an object in a loop and return that object back into its original ...
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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 $\Delta P$: $$ \...
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23 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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1answer
51 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 ...
3
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1answer
73 views

Nesting in Fe-based superconductors

Many studies about iron-based superconductors mention the nesting of Fermi pockets, such as here or here. As far as I understand it it represents some kind of interplay between different Fermi ...
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1answer
50 views

Adiabatic transition from superfluid to Mott insulator?

I have a question about the dynamical passage from superfluid to Mott insulator state in the Bose-Hubbard model. Is it possible to go from superfluid region to the Mott insulator by changing the ...
2
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1answer
62 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} K_{eff}^{(1)}[t_0](t)&=&...
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35 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 ...
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96 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 $SU(2)$?
4
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85 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: $D(E)=2\int_{...
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16 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 T^(-...
4
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1answer
149 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
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2answers
97 views

What is the meaning of the zero point of the real part of the dielectric function for a semiconductor?

I basically understand the zero point of the real part of the dielectric function for a metal. It generally corresponds to plasmon. For a metal, if the frequency is lower, the real part is negative ...
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1answer
52 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 ...
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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?
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1answer
67 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 ...
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1answer
73 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 ...
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1answer
53 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}} <\...
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1answer
53 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 ...
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1answer
90 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} \dfrac{i\omega-\xi_1}{[(i\omega-\xi_2)^2-...
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1answer
53 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 ...
2
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2answers
66 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 $\frac{1}{2}\sum_{i}\sum_{j\...
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1answer
74 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 ...
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1answer
294 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}) =\...
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55 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, ...
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267 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 ...
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1answer
36 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 ...
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1answer
62 views

Elementary question about the quantization of Hall conductivity

In the literature I read that the Hall conductivity is quantized because the Hall conductivity is actually the winding number associated with the mapping from the brillouin zone (a torus) to the space ...
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40 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?
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122 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 ...
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2answers
73 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 ...
2
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2answers
78 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 P\...
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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. $$ n^{(1)},n^{(2)},...=\mathcal{O}(\mathcal{N}) $$ ...
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65 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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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 ...
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0answers
24 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: $$g(\...
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93 views

Transfer from Heisenberg to Ising model

It is well know, that ferromagnets can be described using Hamiltonian $$ H = -\sum\limits_{i<j}J_{ij}\, (\mathbf{s}_i \cdot \mathbf{s}_j). $$ where (three dimensional) spins $\mathbf{s}_i$ ...
4
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1answer
35 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 ...
5
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1answer
107 views

Difference between $\nu=5/2$ quantum Hall state, chiral p-wave superconductor, He 3

I am interested in the relation between the following three phases of matter (in 2D): chiral $p$-wave superconductor (spineless $p_x + i p_y$ pairing) $\nu=5/2$ fractional quantum Hall state A-phase ...
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17 views

What is our most complete microscopic theory for the elastic-plastic transition point?

I suppose its all stated in the title. What is our most successful description of the microscopic behavior of material at the elastic-plastic transition point. My condensed matter physics prof was ...
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40 views

Quantum spin Hall effect and the edge states

In quantum spin Hall effect or Kane-Mele model, how can one get rid off the edge states without affecting the bulk?
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1answer
41 views

behavior of dissolved ionic compounds in an electric field

Consider the following setup - An open, insulating box is filled with distilled water, into which is dissolved a significant amount of pure NaCl. Two insulated lumps of conductor, one with a large ...
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58 views

Electron self-energy calculation for a $k$-dependent interaction

I am trying to calculate the Fock term of an electronic self energy in the Matsubara formalism : Where the straight black line in the free electronic Green's function : $G_{k+q}(i\omega_n + i\nu_n) ...
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28 views

Do tensor product tables for irreducible representations apply for non-symmorphic space groups?

I'm reading Dresselhaus's book on group theory for solid-state physics, but I'm having trouble understanding how to get irreducible representations for phonons away from $\mathbf{k} = \mathbf{0}$ for ...
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30 views

Open-source code for computing response functions

Summing Feynman diagrams to compute the response functions of a microscopic model is common in many areas of physics. While conceptually straightforward, the task can be computationally intensive. ...
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76 views

How to describe spin-orbital coupling in Weyl semi-metal

In three dimensional Weyl semi-metal, the Hamiltonian that describes low excitation quasi-particle is well-know Weyl Hamiltonian: +/- $k\cdot\sigma$. But if I want to add spin-orbital coupling in that ...
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1answer
134 views

Kronecker sum or direct sum?

When we write $$H=\sum_k H_k$$ in condensed matter physics, are we using Kronecker sum or direct sum? I think this is direct sum. However, Wikipedia says it is Kronecker sum. Can anyone give some ...
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27 views

How do phonons and spinwaves interact? [closed]

What governs the coupling of acoustic phonons to transverse and longitudinal spinwaves? Is there a simple picture?
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1answer
130 views

Simple Explanation of Kondo Effect

Does anyone have a simple explanation of the Kondo Effect? (i.e. a simple physical picture + maybe equations to think of?) My current understanding is this: If we consider an electron scattering ...