The study of physical properties condensed phases of matter, including solids and liquids.
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1answer
37 views
Does an Ising lattice that returns to equilibrium create a current by induction?
Consider you have an Ising lattice with a dominant up component out of thermal equilibrium, that's your initial state. The down spins want to flip up and align with the ups, and they'll do so until a ...
5
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1answer
215 views
A question about Haldane's conjecture
Haldane's conjecture states that the integer spin antiferromagnetic Heisenberg chains have a gap in the excitation spectrum. However, the dispersion relation of the antiferromagnetic spin wave is ...
4
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1answer
96 views
What is spin stiffness?
I read the defination of spin stiffness here
But I can't understand how to twist an angle. Any help will be appreciated!
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0answers
60 views
Why do Fermi liquids have T^2 resistivity?
I have often read that metals that are Fermi liquids should have a resistivity that varies with temperature like $\rho(T) = \rho(0) + a T^2 $.
I guess the $T^2$ part is the resistance due to ...
2
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1answer
99 views
How to define the order parameter of the q-state Potts model?
The order parameter of Ising model can be defined as $m=\frac{N_1-N_2}{N}$, if $N$ is the total number of lattice points, $N_1$ and $N_2$ is the number of lattice points spin up and down respectively, ...
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2answers
72 views
What are some ways of inducing spin polarization?
I saw a talk today and they mentioned how nitrogen-vacancy diamond centers can be used to optically induce spin polarization and now I wonder what other ways there are to induce a spin polarization.
...
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0answers
96 views
Wave function ansatz for disclinated graphene with spin
I am currently investigating spin dynamics in disclinated graphene. More information about my approach can be found in my other post. I would like to know if my approach is somewhat correct to find ...
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0answers
71 views
How to charge a field?
In a previous post [ Noether theorem, gauge symmetry and conservation of charge ] we were discussing the different ways to demonstrate the current conservation: via the first Noether theorem applied ...
3
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1answer
65 views
Spin Liquid in a band insulator?
In the literature, spin liquids are only possible in Mott insulators, however, I'm not entirely sure why the nuclear spin can't create a spin liquid in a band insulator.
Is this possible? If so, is ...
3
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1answer
158 views
Why does a superconductor obey particle-hole symmetry?
We normally solve the Bogoliubov-de Gennes (BdG) equations in order to compute the energy spectrum of a superconductor. The Nambu spinor is a common object that is used in formulating these equations. ...
4
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1answer
61 views
Where to learn Temperature Dependent Conductivity induced by Electron-Phonon Interaction? [closed]
I want to learn how to calculate the temperature dependent conductivity induced by electron-phonon interaction.
I know in low temperature, the resistance in metal $\rho$ is proportional to $T^5$, $T$ ...
4
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1answer
203 views
Is edge state of topological insulator really robust？
I am a little confused! Some people are arguing that the gapless edge state of Topological insulator is robust as long as the time reversal symmetry is not broken，while other people say that it is ...
2
votes
1answer
126 views
What are the statuses of Silicene and Graphene for real world circuit production?
A lot of hype is out there about both of them (especially the latter) and I was wondering if there is more concrete information about them other than the news IBM posted on a circuit 2 years ago and ...
2
votes
2answers
161 views
Has BCS Cooper pair condensate been observed in experiment?
Feshbach resonance in s-wave scattering states a BCS Cooper pair condensation at B-field just above the resonance where the scattering length a <0. Just wondering if the condensation has been ...
10
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2answers
353 views
Why quantum hall effect has chiral edge state?
The most popular explaination may be the following: in magnetic field, electrons move in cycolotron orbits, such cycolotron orbits ensure electrons to move in one direction at the edge. That is why ...
2
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0answers
64 views
Electron Relaxation/Polarization for and n-type Semiconductor
Please help me understand the following (general) statement, referring to electrons in a full valence band of an n-type semiconductor:
"An electron filling up the last empty state in the valence band ...
3
votes
1answer
108 views
Graphene with a disclination and the spin-orbit coupling
I am trying to follow the methods used in this paper (http://arxiv.org/pdf/1208.3023.pdf) to construct the Hamiltonian of a graphene cone, but taking into account the spin-orbit coupling.
The paper ...
3
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2answers
148 views
Difference between Monte Carlo and Quantum Monte Carlo methods?
What are the differences between Classical Monte Carlo methods and Quantum Monte Carlo methods in condensed matter physics? If one want to study strongly correlated systems with Quantum Monte Carlo ...
4
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1answer
183 views
Chiral edge state as topological properity of bulk state
As far as I know, quantum hall effect and quantum spin hall effect has chiral edge state. Chiral edge state is usually closely related with delocalization, since back scattering is forbidden. However, ...
3
votes
1answer
102 views
Why FQHE need a lower energy state?
There are a lot papers explaining why Laughlin's wavefunction are energetically favorable, but seldom explain why a lower energy state could explain the plateau at $\nu=1/3$. I met at several places ...
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0answers
93 views
Ground and first excited state of non interacting spin system Hamiltonian
For a non interacting spin system containing two $\frac{1}{2}$ spin particles I am trying to determine its Hamiltonian. If the energy of a up spin is $+\mu {\bf B}$ and a down spin is $-\mu {\bf B}$, ...
2
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3answers
118 views
How to judge whether a symmetry will be spontaneously broken while only given a Hamiltonian preserving this symmety
As asked in the title, is Hamiltonian containing enough information to judge the existence of spontaneously symmetry breaking?
Any examples?
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1answer
87 views
Ground states of the Hamiltonian of a two spin system
For the spin system shown in this graph (http://i.stack.imgur.com/3lg1R.png), the Hamiltonian is $$S^{(1)}_z\cdot S^{(1)}_z=\frac{1}{4}\begin{pmatrix}
1 & 0 &0 &0 \\
0&-1 &0 ...
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1answer
283 views
Why path integral approach may suffer from operator ordering problem?
In Assa Auerbach's book (Ref. 1), he gave an argument saying that in the normal process of path integral, we lose information about ordering of operators by ignoring the discontinuous path.
What did ...
3
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1answer
162 views
Zero Resistance in Quantum Hall Effect and Superconductivity
What is the difference between the zero resistance of $R_{xx}$ in integer quantum Hall effect and the zero resistance in superconductivity?
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1answer
114 views
Hamiltonian of a simple graph
I have a spin system:
As shown in the picture, there are two spins S1 and S2, and a pair of interactions between them. One is a ferromagnetic interaction and the other is anti ferromagnetic ...
2
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2answers
303 views
Partially filled orbitals and strongly correlated electrons
Interesting behavior of strong correlation between electrons occur in metals with partially filled d or f orbitals (transition metals). Why these strong correlations do not appear with elements with ...
4
votes
1answer
75 views
Derivatives of fluctuations about a condensate
Firstly I am not sure as to whether I am using the word "condensate" in the right context. In QFT contexts I think I see it getting used to mean the space-time independent solution which would solve ...
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1answer
60 views
The orthogonalized plane waves
An orthogonal plane wave with wave number $k$ is written as
$$ OPW_k=e^{ ik\cdot r}-\sum_\alpha \psi_\alpha(r) \int \psi^*_\alpha (r'') e^{ik\cdot r''} d\tau'',$$
where index $\alpha$ and $k$ ...
4
votes
1answer
237 views
What does “particle number conservation” mean in condensed matter physics?
What exactly does it imply about a condensed matter system to have particle number conserved or not conserved?
For example, why does the superconducting phase break particle number conservation while ...
2
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0answers
188 views
condensed matter physics must reads [closed]
Possible duplicate:
Books for Condensed Matter Physics
I'm looking to learn more about cutting edge research in condensed matter theory.
I hope you'll help me find some recommended articles in ...
2
votes
3answers
141 views
Bose-Einstein condensation in systems with a degenerate ground state
I understand that when a system enters the BEC phase a sizable fraction of the total number of particles enters the ground state, until at some point almost all of your particles are in the ground ...
19
votes
5answers
2k views
Do photons gain mass when they travel through glass?
Please correct me if I'm wrong, but I believe that photons slow down when travelling through glass. Does this mean they gain mass? Otherwise, what happens to extra kinetic energy?
I understand now ...
4
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2answers
115 views
Crystal Angular Momentum
In a crystal, we don't have full translational symmetry, but we still have discrete translations. This allows us to define "crystal momentum" that is conserved modulo a reciprocal lattice vector.
In ...
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1answer
78 views
In the big crunch theory, when the big crunch singularity forms, can the resulting black hole decay through hawking's radiation?
I've been pondering about this and I couldn't really find the answer for this. The big crunch theory postulates that the universe will eventually stop expanding and reverse back in on its self into a ...
2
votes
1answer
115 views
Crystal magnetic response only skin deep?
The Hamiltonian for a single electron in a magnetic field reads
$$H=\left(\frac{{\bf p}^{2}}{2m_{e}}+q_{e}\phi\right)+\mu_{B}\left({\bf \hat{L}}+g{\bf \hat{S}}\right)\cdot{\bf ...
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0answers
21 views
What favors island growth of a sputtered material?
What would be the best choice of parameters in general if one would like to get pure island growth (i.e. Volmer-Weber growth) in a sputtering deposition process and what would be a good estimate of ...
6
votes
2answers
164 views
Is the speed of sound almost as high as the speed of light in neutron stars?
Have you ever wondered about the elastic properties of neutron stars?
Such stars, being immensely dense, in which neutrons are bound together by the strong nuclear force on top of the strong gravity ...
2
votes
1answer
135 views
What happens to atoms inside the black hole?
Black holes have very high gravitational force intending to crush everything. So as we know atoms in a molecule have inter atomic spacing between then and further electron,s also revolve at a certain ...
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vote
1answer
69 views
Dynamic structure factor
Dynamic structure factor is the spatial and temporal Fourier transform of Van Hoves time dependent pair correlation function. It is written as
$$ S(k,\omega)= \frac{1}{2\pi}\int F(k,t)\exp(i\omega ...
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0answers
107 views
Phonon Momentum
I am reading Charles Kittel's solid state physics and wondering what's the mechanism that neutron waves and photons can interact with phonons and the process obey the generalized momentum-energy ...
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2answers
206 views
Is the index of refraction dependent on the wavelength of light?
I just read in some class notes for a crystallography class that there are no refractive lenses for X-rays because the index of refraction of most materials is close to 1. Is the index of refraction ...
1
vote
2answers
137 views
Typical operators in tight binding
Let the tight-binding Hamiltonian be $\sum\limits_{ij} {{t_{ij}}\left| i \right\rangle \left\langle j \right|}$. Where ${\left| i \right\rangle }$ is the atomic orbit at lattice site $i$.
My question ...
2
votes
1answer
69 views
Phonon wavevector $q\le 2k_{F}$ for Electron-Phonon Scattering
I am reading "Supercollision cooling in undoped graphene." There the authors write: ``Above $T_{BG}$ (the Bloch-Gruneisen temperature), only a fraction of acoustic phonons with wave vector $q\le ...
1
vote
1answer
104 views
Semi-conductor band-gap and deformation potential
Submitting a semi-conductor to stress leads to a deformation in the energy-bands, roughly described by:$$H_{ij} = {\cal{D}}_{ij}^{\alpha\beta}\;\epsilon_{\alpha\beta}$$
$\epsilon$ being the strain ...
2
votes
1answer
109 views
Rewriting Creation and Annihilation Operators
I am playing with the Landau Level problem and Algebraic solutions to it. I am given
$$a=\frac{l_{b}}{\sqrt{2}\hbar}(\pi_{x}-i\pi_{y}) ...
1
vote
2answers
230 views
Why should the Fermi level of a n-doped semiconductor be below the one of a p-doped?
In a pn-junction, the difference in Fermi level between the p doped and the n doped regions causes the apparition of a built-in electric field at equilibrium. This electric field goes from the n to ...
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0answers
29 views
Residual symmetries of the superposition of two fcc lattices
Fcc lattices are Bravais lattices and so are invariant under a set of discrete translations plus inversions over the 3 axis ($x\rightarrow -x$,$y\rightarrow -y$,$z\rightarrow -z$). When one superposes ...
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vote
1answer
138 views
Double-counting correction in a LDA + DMFT calculation
To theoretically study correlated materials, one usually has to consult to the LDA + DMFT calculations, in which the two-particle interaction is usually double-counted. A general recipe for the ...
3
votes
1answer
271 views
Validity of Bogoliubov transformation
In condensed matter physics, one often encounter a Hamiltonian of the form
$$\mathcal{H}=\sum_{\bf{k}}
\begin{pmatrix}a_{\bf{k}}^\dagger & a_{-\bf{k}}\end{pmatrix}
\begin{pmatrix}A_{\bf{k}} ...
