The study of physical properties condensed phases of matter, including solids and liquids.
6
votes
1answer
156 views
Spin-ice materials with strong quantum fluctuations
Spin-ice materials are insulating materials where
spins form a 3D pyrochlore lattice and have a frustrated magnetic interaction. The spin dynamics in most spin-ice materials
is very classical and has ...
8
votes
1answer
1k views
Spontaneous Time Reversal Symmetry Breaking?
It is known that you can break P spontaneously--- look at any chiral molecule for an example. Spontaneous T breaking is harder for me to visualize. Is there a well known condensed matter system which ...
6
votes
1answer
196 views
Ground state degeneracy of a variation of Toric Code model
We know that the ground state degeneracy of Toric Code model is 4. An easy way of seeing this is the following:
Consider a 2D spin model where all the spins live on the links. The Hamiltonian is ...
7
votes
1answer
564 views
Is resonating valence bond (RVB) states long-range entangled?
Quantum liquid is at the core of condensed matter theory study, examples include superfluid in Bose Hubbard model, quantum spin liquid around the RK point of a quantum dimer model, string-net ...
7
votes
0answers
189 views
How to determine if an emergent gauge theory is deconfined or not?
2+1D lattice gauge theory can emerge in a spin system through fractionalization. Usually if the gauge structure is broken down to $\mathbb{Z}_N$, it is believed that the fractionalized spinons are ...
5
votes
0answers
169 views
Quasi 1D insulators with strong spin-orbital interaction
We know that the spin-1 chain realizes the Haldane phase which is an example of
symmetry protected topological (SPT) phases (ie short-range entangled phases with symmetry). The Haldane phase is ...
4
votes
0answers
153 views
Significance of Dirac cones in condensed matter physics
In condensed matter physics, Dirac cones can be found in graphene, topological insulators, cuprates, and iron-pnictides. This means that electrons behave as massless particles near the Dirac points.
...
7
votes
2answers
450 views
Majorana zero mode in quantum field theory
Recently, Majorana zero mode becomes very hot in condensed matter physics.
I remember there was a lot of study of fermion zero mode
in quantum field theory, where advanced math, such as index ...
17
votes
10answers
1k views
What is spontaneous symmetry breaking in QUANTUM systems?
Most descriptions of spontaneous symmetry breaking, even for spontaneous symmetry breaking in quantum systems, actually only give a classical picture.
According to the classical picture, spontaneous ...
3
votes
0answers
295 views
Goldstone modes and Heisenberg model
The ideia is to show that, because of Goldstone modes, 2d systems are quite different from 3d ones. So, considering the Heisenberg model, I'll post here what I'm asked to and my current thoughts on ...
4
votes
1answer
587 views
What is the relationship between string net theory and string / M-theory?
I've just learned from this one of Prof. Wen's answers that there exists a theory called string net theory. Since I've never heard about this before it picks my curiosity, so I`d like to ask some ...
5
votes
1answer
270 views
Graphene Moebius Strip
I'm refering to the Paper:
PHYSICAL REVIEW B 80, 195310 (2009)
"Möbius graphene strip as a topological insulator"
Z. L. Guo, Z. R. Gong, H. Dong, and C. P. Sun.
The paper is also available as a ...
1
vote
1answer
982 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
252 views
Helium-4 superfluidity and gauge symmetry breaking
Is there an accessible account of superfluidity in Helium-4 as a manifestation of "global gauge symmetry" breaking?
And what is meant by "global gauge symmetry"? I was taught that gauge symmetries ...
4
votes
1answer
344 views
Hit a bottle of beer on the top with another causes the first to spit all the gas, why?
So, on the other day me and my colleges were discussing the following phenomena:
Pick two open bottles of beer. With the bottom of the first, hit the second on the bottleneck, in the following way: ...
1
vote
2answers
101 views
Reference needed for Iron-based superconductors
Iron-based superconductor is a class of high-$T_c$ superconductors discovered in 2008.
Are there any review papers about these superconductors yet? If not, which are the key papers in the field?
3
votes
0answers
83 views
Qualitative argument to determine energy of defects
In a book of "LES HOUCHES - Critical Phenomena, Random systems, Gauge theories" the author Frolich says that:
2D
In two dimensions, the mean energy of an isolated point defect in a square area of ...
8
votes
1answer
382 views
Interpretation of the Random Schrödinger Equation
I should preface this by admitting that my physics background is rather weak so I beg you to keep that in mind in your responses. I work in mathematics (specifically probability theory) and a paper ...
3
votes
1answer
117 views
How is the dynamic equilibrium nature of fermi-dirac distribution of particles facilitated?
I read this in Kittel: Introduction to Solid State Physics about deriving that product of electron and hole concentration as independent at a given temperature by the law of mass action.
For this ...
6
votes
0answers
434 views
10 Big Problems - Condensed Matter [closed]
I think it was Feynman that suggested that you should always carry ten big problems around in your head, and when you encounter a new method, see whether this new method allows you to make progress on ...
2
votes
1answer
85 views
What is the difference between contact-limited and space-charge-limited charge transport?
I am reading a paper ("Tunable Electrical Conductivity of Individual Graphene Oxide Sheets Reduced at 'Low' Temperatures," Jung, et al. Nano Lett. 2008, 8, 4283-4287) about electrical conductivity in ...
2
votes
1answer
191 views
Fractional statistics
A common way to show that anyons exhibit fractional statistics in 2D is by arguing that the paths of two anyons winding round each other cannot be continuously deformed to zero. This seems to assume ...
4
votes
1answer
504 views
The Difference between Thomas-Fermi Screening and Lindhard Screening
Assuming the general theory of screening related to electron-electron interactions, I was wondering if anyone could provide a clear, yet conceptually complete explanation of the differences between ...
2
votes
3answers
311 views
Gauge invariance and form of the vacuum polarization tensor
In quantum field theory or condensed matter physics, the fermionic one-loop diagram gives rise to the polarization tensor
$$ Π^{µν} = Tr[ γ^µ G γ^ν G ] $$
If we couple the electrons to an ...
1
vote
1answer
72 views
Relative Change of Volume
Simple question, in materials publications I often see the relative change of volume in a system reported as
$$ \Delta \left (V \right )/V $$
is the denominator volume supposed to be initial or the ...
4
votes
3answers
407 views
Entanglement spectrum
What does it mean by the entanglement spectrum of a quantum system? A brief introduction and a few key references would be appreciated.
2
votes
2answers
302 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 ...
5
votes
1answer
250 views
Analytic continuation of imaginary time Greens function in the time domain
Consider the imaginary time Greens function of a fermion field $\Psi(x,τ)$ at zero temperature
$$ G^τ = -\langle \theta(τ)\Psi(x,τ)\Psi^\dagger(0,0) - \theta(-τ)\Psi^\dagger(0,0)\Psi(x,τ) \rangle $$
...
4
votes
1answer
508 views
Tight Binding Model in Graphene
I'm following a calculation done by a guy who's done it a bit different than what I've done before (used nearest neighbour vectors and a DFT instead of what I will show below), I'm not quite sure how ...
1
vote
2answers
105 views
Quantization of momentum in nanotubes
I'm reading about carbon nanotubes and how the momentum (lets call it $k_x$) is quantized along the circumferential direction and not along the cylindrical (call this $k_y$). I can follow the maths ...
2
votes
1answer
552 views
Which ferromagnetic material has the lowest Curie temperature?
It is hard to search for materials by their properties in general and I am trying to find a material with a very low Curie temperature. At the moment I am browsing different sites but can only find a ...
2
votes
2answers
286 views
Has Bose-Einstein theory been considered for dark matter?
Has Bose-Einstein theory been considered for dark matter?
The theory would explain why no measurable radiation is emitted due to zero temperature--its lack of interaction with other matter and its ...
4
votes
1answer
153 views
What is replica symmetry breaking, and what is a good resource for learning it?
M. Mezard, G. Parisi and coworkers have written about replica symmetry and its breaking in spin glasses, structural glasses, and hard computational problems.
I am just getting acquainted with this ...
5
votes
2answers
580 views
Basic Question - Green's Functions in Quantum Mechanics
I am trying to learn about Green's functions as part of my graduate studies and have a rather basic question about them:
In my maths textbooks and a lot of places online, the basic Greens function G ...
2
votes
1answer
202 views
Change in Vapour/Liquid change point, at very low pressure
In a previous question, I was given an answer:
"A quick Google suggests that the triple point of Hydrogen is 13.8K and the triple point of Neon is 24.6K, so neither can exist as liquids at ...
2
votes
1answer
595 views
Time-reversal symmetry
For a quantum system with time-reversal symmetry, other than the absence of a magnetic field, can we infer anything else about the system?
1
vote
1answer
239 views
Helium plasma in space and its properties
It is said, that, "Most of the Helium in the Universe, is in a plasma state".
Plasma's are now talked of, as the forth state of matter, but this does not seem to be a majority opinion. Plasma's are ...
3
votes
3answers
211 views
Does Helium just naturally display BEC properties at <1K, or does it become a BEC?
I am researching low temperature, near absolute zero, and in particular Bose Einstein Condensate. There is a lot of research information, but it is confusing, and not explained. Technically a BEC is ...
5
votes
2answers
257 views
Transition between 2D and 3D quantum systems
Quantum Hall effect and anyonic particles are examples that occur in a two-dimensional system. However, experiments for such systems can only be realized in a pseudo-2D environment, where the third ...
2
votes
3answers
352 views
Incompressible quantum liquid
In condensed matter physics, what does the term incompressible in incompressible quantum liquid mean?
3
votes
4answers
999 views
Books for Condensed Matter Physics
What are some good condensed matter physics books that can fill the gap between Ashcroft & Mermin and research papers? Suggestions for any specialized topics (such as superconductivity, CFT, ...
2
votes
0answers
72 views
Factorization of fermionic scattering integral in 2d momentum rep
the scattering integrals for fermions involves both momentum ($k$) and energy ($k^2$) conservation and a nonlinear phase space factor of a distribution function $f(k)$.
$$\begin{multline}I(k) = ...
15
votes
3answers
891 views
Are elementary particles actually more elementary than quasiparticles?
Quarks and leptons are considered elementary particles, while phonons, holes, and solitons are quasiparticles.
In light of emergent phenomena, such as fractionally charged particles in fractional ...
2
votes
1answer
163 views
True Ground State Population of Ideal Bose-Einstein Condensate at Critical Temperature
I'm supposed to demonstrate that although we make the assumption in an ideal BEC that the ground state population follows
$N_0 = N\left[1-\left(\frac{T}{T_c}\right)^{3/2}\right]$
in reality the true ...
8
votes
1answer
302 views
Kramer's-Kronig relations for the electron Self-Energy Σ
I'm currently studying an article by Maslov, in particular the first section about higher corrections to Fermi-liquid behavior of interacting electron systems. Unfortunately, I've hit a snag when ...
7
votes
3answers
356 views
Mathematical rigorous introduction to solid state physics
I am looking for a good mathematical rigorous introduction to solid state physics. The style and level for this solid state physics book should be comparable to Abraham Marsdens Foundations of ...
5
votes
2answers
260 views
Reduction of a sum to the first Brillouin zone in a band structure calculation
this might be a "standard trick" for many solid state physicists,
however it's one that I'm not familiar with so maybe you can help me.
Here's the Problem:
Suppose we're given a Hamiltonian of the ...
2
votes
1answer
147 views
Negative energies and a partition function
I'm writing down the partition function for a system, for which I know the dispersion relation
$$E \left( \mathbf{k} \right) = \sqrt{ \left| \mathbf{k} \right|^2 + m^2 + \cdots }$$
The exact form is ...
3
votes
1answer
183 views
What are Low-lying energy levels?
I am reading about some canonical transformations of the Hamiltonian (of a system consisting of an electron interacting with an ionic lattice) due to Tomanaga and Lee, Low and Pines. One of the ...
6
votes
1answer
159 views
Thermodynamic limit “vs” the method of steepest descent
Let me use this lecture note as the reference.
I would like to know how in the above the expression (14) was obtained from expression (12).
In some sense it makes intuitive sense but I would ...
