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

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2answers
548 views

What is the experimental status of AdS/CFT, AdS/QCD, AdS/CMT, etc?

What experiments have challenged or supported AdS/QCD, AdS/CMT, etc? What experiments should we look forward to do this?
4
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2answers
446 views

Why is a critical system equal to a gapless system?

In condensed matter physics, people often say that a system without energy gap is a critical system. What does it mean? Any help is appreciated!
3
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0answers
131 views
2
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1answer
748 views

Intuitive description of what a “Fermi Gas” really is?

This question is based in the area of material equations of state. I am wanting to know what a Fermi Gas really is. I have searched in several places for a decent description, but I have not found ...
8
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1answer
272 views

Chiral coupling in string-nets

In Xiao-Gang Wen's review of topological order http://arxiv.org/abs/1210.1281 , he states in footnote 52 that string-nets are so far unable to produce the chiral coupling between the SU(2) gauge boson ...
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1answer
187 views

Is there real materials have Lieb lattice structure? [closed]

Is there real materials have Lieb lattice structure? Some examples?
3
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2answers
166 views

Equivilence of One Flux Quantum and Zero Flux

In Ady Stern's review of the Quantum Hall effect, he says of a quantum hall system "The spectrum at $\Phi = \Phi_0$ is the same as the spectrum at $\Phi = 0$..." Can someone explain why this is? It ...
4
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1answer
584 views

Does a quantum phase transition have latent heat?

As the title says, I am thinking about the question that whether a quantum phase transition has latent heat. If so, at 0 temperature, we can drive the system by some parameter from disorder phase to ...
1
vote
0answers
83 views

the poles of impurity system's Green's function

Denote the pure system as system 1, with both continuum and discrete eigen energy. $G_0$ is its Green's function. After introducing some impurities, we call the resultant system system 2 with new ...
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0answers
377 views

Gauge invariance in Laughlin's argument

In Laughlin's gedanken experiment which aims to explain quantization of Hall conductance, one takes the adiabatic derivative of the Hamiltonian with respect to vector potential. Now it seems that it ...
3
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1answer
2k views

What is the Hubbard-Holstein model?

Please explain as simply as possible what the Hubbard-Holtstein model is and what it is used for.
5
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1answer
250 views

Measurement of topological spin

How do you measure the topological spin of an anyon? So how could an experimental setup look like? Is topological spin an observable at all?
7
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1answer
271 views

Simulating the evolution of a wavepacket through a crystal lattice

I am interested simulating the evolution of an electronic wave packet through a crystal lattice which does not exhibit perfect translational symmetry. Specifically, in the Hamiltonian below, the ...
7
votes
1answer
133 views

Two-fluid description of superfluidity

I'm trying to teach myself about superfluidity and I'm slightly confused on the ''two-fluid'' description. From what I understand, the superfluid is considered to be a mixture of two fluids, a ...
3
votes
3answers
280 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 ...
6
votes
1answer
288 views

String-net condensation in 3D

In 2D and 3D quibit models, string-net condensation can happen. In 3D or higher models, is it possible for surfaces (instead of just strings) to condense?
6
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1answer
2k views

What conductance is measured for the quantum spin Hall state when the Hall conductance vanishes?

It's probably just a definition, but what did König et al. actually measure when he confirmed the existence of surface states in CdTe/HgTe/CdTe quantum wells (see http://arxiv.org/abs/0710.0582)? ...
3
votes
1answer
5k views

Optical constants of noble metals: the Drude model for microwave modelling

I have a question regarding the optical constants of noble metals. According to Johnson and Christy's paper Optical Constants of Noble Metals (Phys. Rev. B 6, 4370–4379 (1972), ...
4
votes
3answers
4k views

Physical meaning of magnetic length

What is the physical meaning of magnetic length $\ell_B=\frac{\hbar c}{e B}$ in 2D electron system under magnetic field? When $\ell_B \longrightarrow a$, where $a$ is the lattice constant, does that ...
14
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7answers
806 views

Optical equivalent of a superconductor

Is there some material state that can propagate light indefinitely without dissipation or absorption, like superconductors are able to transmit current indefinitely? If not, then the question is, why ...
10
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1answer
542 views

Is the liquid/solid line infinite?

Starting from the triple point, is the melting line between solid-phase and liquid-phase infinite? If not, why does it end? Because pressures are so high that classical inter-molecular interactions ...
9
votes
1answer
304 views

Lagrangian for Goldstone mode + topological excitation

The XY-model Hamiltonian is the following, $${\cal H}~=~-J\sum_{\langle i,j\rangle} \cos (\theta_i -\theta_j).$$ The Goldstone mode corresponds to term $(\nabla \theta)^2$ in the effective ...
-1
votes
1answer
793 views

Why do phonons cause excellent heat conduction in diamonds?

Phonons are the quantum of lattice vibrations in crystals and are not to be confused with photons, the gauge bosons of the electromagnetic force. Apparently, they contribute to heat conduction, but I ...
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0answers
35 views

Impurity scattering [duplicate]

Possible Duplicate: Impurity scattering temperature dependence Is there any temperature dependence of relaxation time in impurity scattering of conducting electrons? It seems to me that ...
8
votes
2answers
5k views

How is the topological $Z_2$ invariant related to the Chern number? (e.g. for a topological insulator)

This question relates to the $Z_2$ invariant defined e.g. for topological insulators: Is it correct to relate $Z_2$ = 1 to an odd Chern number and $Z_2$ = 0 to an even Chern number? If yes, is it ...
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0answers
189 views

Are there any good reading materials for variational approach in many-body theory? [closed]

I need something like a summary of existing results, including the treatment of BCS Hamiltonian and Hubbard model. Auerbach's book is a good one but I still hope to get more comprehensive review. My ...
7
votes
2answers
5k views

Fermi surface nesting and CDW/SDW/SC orders

Fermi surface nesting and CDW/SDW/SC orders. What is the definition of a nesting vector? And why Fermi surface nesting gives rise to different orders at $T=0$? (CDW: charge density wave; SDW: spin ...
3
votes
1answer
984 views

Chern number in condensed matter physics

In mathematics, the Chern number is defined in terms of the Chern class of a manifold. What is the exact definition of Chern number in condensed matter physics, i.e. quantum hall system?
6
votes
2answers
385 views

Meissner Effect for Type-II Superconductors

I was wondering whether the breakdown field strength for the Meissner effect may be attributed to the Zeeman effect? I can see the latter (along with the Stark effect) to be more analogous to electron ...
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0answers
87 views

Asking for references on the variational treatment of spin wave

My idea is the following: We have a system with Hamiltonian $H$, and we know that there is spin wave in this system by some symmetry-breaking arguments. Now we start from the ground state ...
0
votes
2answers
3k views

What is Curie-Weiss temperature?

What is Curie-Weiss temperature? What is the difference between Curie-Weiss temperature and Curie temperature?
1
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1answer
273 views

About Efimov States and Halo-Nuclei

I read that Halo nuclei could be seen as special Efimov states, depending on the subtle definitions. (The last sentence in the second to last paragraph of this Wikipedia article.) This does ...
3
votes
0answers
598 views

Simple model of edge states for a two-dimensional topological insulator

Quantum spin Hall states or, topological insulators are novel states of matter that have insulating bulk and gapless edge states. Are there any simple models that show these features? See e.g. the ...
3
votes
1answer
1k views

What is different between resolvent and green function

I bumped into a book, where Resolvent $R^{\pm}(E)$ is defined as $e^{\mp iHt/\hbar}=\pm\frac{i}{2\pi}\int_{-\infty}^{\infty}dER^{\pm}(E)e^{\mp iEt/\hbar}$ and $R^{\pm}(E)=\frac{1}{\pm ...
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0answers
277 views

Where can I find a complete list of metamaterials up to today?

Where might I find a list of all the metamaterials up-to-date?
3
votes
1answer
259 views

$J_1$-$J_2$ Heisenberg antiferromagnet

In this paper, the authors solve for the excitation spectrum in a $J_1$-$J_2$ Heisenberg antiferromagnet using the modified spin-wave theory in the Dyson-Maleev representation. As an intermediate ...
4
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1answer
591 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
119 views

How to derive the divergence leading to Kohn anomalies?

I'm trying to understand the mathematical derivation given in the book "A Quantum Approach to Condensed Matter Physics" on page 215 (see 1), for explaining how the phonon-energy perturbed by ...
10
votes
2answers
996 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
votes
1answer
48 views

Variational approach to search the excitations. What will happen if start from wrong reference state?

By 'wrong reference state' I mean a state which cannot be transformed into desired ones via variational ansatz $\left|\Psi\left[\mathbf{n}\right]\right\rangle ...
1
vote
2answers
1k views

Applications of QFT in theoretical physics

I would like to know which fields in physics have seen growth or benefited by applying QFT? I know that approaches to quantum gravity such as string theory use QFT, HEP and also some branches of ...
11
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0answers
2k views

Griffiths phase

What are Griffiths effects in the context of condensed matter physics? From a cursory examination of the literature I've gathered the following: it seems that ordered systems have a "clean" critical ...
2
votes
1answer
116 views

What papers detail the early research on heavy fermion superconductors?

Can someone point me to the papers detailing when/where/how heavy fermion superconductors were first synthesized, tested and documented?
3
votes
2answers
690 views

Thomas-Fermi approximation and the dielectric function (+ small bit on graphene)

1) With the dielectric function, which is a function of wavenumber and frequency,how is it possible to take the limit of either to zero without changing the other one? I thought that frequency and ...
3
votes
2answers
255 views

Many faces of linear response theory

I have seen two forms of linear response: One is in the calculation of susceptibilities using Green functions. The other is in the evaluation of response currents, say, London current of a ...
2
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1answer
2k views

What's the differences among the concepts: binding energy, cohesive energy and formation energy?

In the papers about first principles (or ab initio) calculations, there are three energies which are often calculated: "binding energy", "cohesive energy" and "formation energy". Their meanings are ...
4
votes
2answers
556 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 ...
6
votes
2answers
1k views

Why are Topological Superconductors hard to make?

Topological insulators (TI) have already been made in lab. Topological superconductors (TSC), being close cousins of TI, seem harder to make. Why is that? It seems that materials in connection with ...
1
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1answer
851 views

vacuum level alignment

When two materials are connected like the case in heterojunctions, we always firstly align the so called vacuum level[1], and then decide the relative position of other energy levels like conductance ...
0
votes
1answer
326 views

Why is the spinor wave function of graphene what it is?

Why is the spinor wave function of graphene $[e^{-i\theta/2}, e^{i\theta/2}]$? Could it be $[e^{-i\theta/}, 1]$?