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

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Elementary introduction to (quantum) hall effect

Where can I find an elementary introduction to classical and quantum hall effect? Only physics I know is some basic quantum mechanics, EM and statistical physics. My goal eventually is to understand ...
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384 views

Why does chalk dust stick to a chalkboard?

I understand that friction causes the chaos dust to come off the stick of chalk, but what exactly is causing the chalk dust to stay on the chalk board until rubbed off?
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37 views

If I know how many atoms I have in a film, can I know the total magnetic moment?

Say I have a Co film and I know its volume so I know the total number of atoms in it. Using this plus the knowledge that each atom has a magnetic moment of 1.7 Bohr magnetons, would the total magnetic ...
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96 views

Why does the diffusion pole universally appear in the two-particle Greens function (diffuson)

I've been thinking about the calculation of the diffuson in the context of impurity-averaged Greens functions. If you calculate the two-particle Greens function in the ladder approximation (for ...
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541 views

Some questions about anyons?

(1) As we know, we have theories of second quantization for both bosons and fermions. That is, let $W_N$ be the $N$ identical particle Hilbert space of bosons or fermions, then the "many particle" ...
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124 views

Is surface plasmon Fermion or Boson?

When photons are converted into surface plasmon in some artificially designed structure such as metal gratings to provide the additional momentum, is the boson character of photons are preserved or ...
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134 views

Exact Diagonalization of a BdG Hamiltonian on a Finite Lattice

I would like to numerically find the edge modes of a $p_x$ + $i p_y$ BdG Hamiltonian. The lattice version is given by H = $\sum\left[-t \left(c_{m+1,n}^{\dagger} c_{m,n} + \text{h.c} \right) - t\left(...
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81 views

How to perform stroboscopic measurements for Floquet topological insulators?

Floquet topological insulators (arXiv:1008.1792, arXiv:1211.5623) have attracted much research interests in condensed matter physics. The goal is to realize topological insulators from trivial ...
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What observables are indicative of BCS Cooper pair condensation?

What observables are indicative of BCS Cooper pair condensation? "Thought" experiments and "numerical" experiments are allowed. This question is motivated by the question Has BCS Cooper pair ...
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435 views

How are lattice parameters determined from reciprocal space maps?

It seems that the papers speak of reciprocal space maps with very high praise because of its ability to study strain in epitaxial films and determine the amount of relaxation. Also one can determine ...
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166 views

Mathematical proof that $\exp(-1/|g|)$ is always related with formation of bound states through scales?

I know that this function ($g$ means coupling) is non-analytical in $g=0$, so this function is only appreciable under non-perturbative calculations, so is a non-perturbative phenomena. This function ...
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44 views

Fermi Surfaces meeting

I know the fermi level is the highest energy level in an atom for its electrons and the fermi surface is (in reciprocal space) a sphere of radius fermi level, if that makes sense. So when two ...
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172 views

Mean field approach to toric code

Toric code is one of the few exactly solvable model in condensed matter, however, like the paper (http://arxiv.org/abs/1104.5485) that uses SU(2) slave fermion to "solve" Kitaev's honeycomb model, is ...
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1k 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 theorem,...
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108 views

What is the importance of the biquadratic interaction in the AKLT model?

The AKLT in a spin-1 Heisenberg chain can be realized when we introduce the bi-quadratic exchange interaction in addition to the bi-linear interaction. I would like understand this interaction more ...
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229 views

Can a nondegenerate fermionic topological Mott insulator (TMI) state support an emergent bosonic topological order?

Based on my recent study and motivated by a recent paper, I have a naive question. Consider a 2d Hubbard model for electrons at half filling $H=\sum c_k^\dagger h_k c_k+U\sum n_{i\uparrow }n_{i\...
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51 views

Why is there no electric field in the Hamiltonian for the quantum Hall effect?

I was looking at the quantum Hall effect and have a question: The Hamiltonian we use has no electric field in it, but we say there is an electric field along the $y$-axis. Why are we not including ...
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105 views

Particle Hole Transformation of Hamiltonian

The particle hole transformation for a bipartite lattice $\Lambda$ (with sublattices $A$ and $B$) can be written as $$U^\dagger c_{i,\uparrow} U = \epsilon(i) c^\dagger_{i\uparrow} \\ U^\dagger c_{i,\...
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75 views

${\phi}^4$ description of Ising ferromagnet

Suppose the coupling between two spins is $C_{i,j}<0$, then the classical partition function is given by $$Z=\sum_{\{s_i\}}e^{\sum_{i,j}s_iK_{ij}s_j+h\sum_{i}s_i}$$ where $K_{ij}=-\beta C_{ij}$ and ...
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198 views

Proof that a traceless strain tensor is pure shear deformation

How can i proove that the traceless part of linear strain tensor $e$ in the Euler description: $$e_{i,j}={ 1 \over 2 } \left({ \partial u_i \over \partial x_j}+{ \partial u_j \over \partial x_i} \...
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102 views

Dualities in 2+1D lattice gauge theories

A nice way to understand $\mathbb{Z}_2$ gauge theories is via duality transformations. For example, it is illustrated in http://arxiv.org/abs/1202.3120 that a $\mathbb{Z}_2$ gauge theory (with Ising ...
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419 views

Can I integrate out the fermion field that is not gapped?

This piece of argument has been repeated again and again by experts, that is Since the fermions are gapped, then I can integrate it out. but I have no idea of what will happen if the fermions ...
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133 views

Why does the characteristic curve (V vs I) for a light bulb backbend?

When teaching Ohm's Law, I have students do an exploration of a small, incandescent light bulb with a low frequency (1-2 Hz) sine wave. It's a simple series circuit of source and light bulb, ...
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50 views

Question(s) Regarding the Lindhard Function

As a theoretical chemist, I'm slightly outside of my element on a project my advisor gave me, so I come to your for help and direction. Basically, he wants me to integrate the imaginary part of the ...
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48 views

electron shell jumping in Iron?

I understand a "little" about electron shell jumping, I was wondering about "Iron", If iron was heated to a gas, perhaps held in a vacuum maybe even under pressure, would the added energy make the ...
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59 views

Proof of periodicity of Floquet Green's function

It is claimed in many papers that the two-time Green's function in time periodic Hamiltonian case is periodic in the average time, i.e. \begin{equation} G(t+T,t'+T)=G(t,t') \end{equation} when $H(t+...
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527 views

Symmetry arguments for valley physics in graphene with broken inversion

I am trying to understand this paper: http://link.aps.org/doi/10.1103/PhysRevLett.99.236809 (Here is an arXiv version: http://arxiv.org/abs/0709.1274) In the introduction, they mention certain ...
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460 views

Finding the ground state of the toric code Hamiltonian

How do I write by proof, the ground state of the toric code (by Kitaev) Hamiltonian $ H=-\sum_{v}A(v)-\sum_{p}B(p) $ where $A(v)=\sigma_{v,1}^{x}\sigma_{v,2}^{x}\sigma_{v,3}^{x}\sigma_{v,4}^{x}$ and ...
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91 views

Charge and spin susceptibility in the random phase approximation

In the random phase approximation, the charge and spin susceptibility (of a Hubbard model, for example) can be written as $$\chi^c(q) = \chi^0(q)\left[1+U^c\chi^0(q)\right]^{-1},$$ $$\chi^s(q) = \...
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25 views

Energy magnetization in the presence of temperature and chemical potential gradient

In the following paper (Phys. Rev. Lett. 97, 026603) http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.97.026603 the energy magnetization part of the energy current is given in the presence ...
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507 views

Naive questions on the ground states of Kitaev model

I got some naive questions on the ground states of honeycomb Kitaev model (with open boundary conditions): (1) Consider a simple case that $J_x=J_y=0$, then the model reduces to $$H=J_z\sum_{z\text{ }...
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118 views

Is there a bulk signature of topological nontriviality for a 3D free fermion band insulator?

Is there such thing as a 3D Chern invariant (or some other quantity) that I can use to test an insulating quasiparticle spectrum is a topologically trivial or non-trivial insulator? Does one exist ...
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2answers
95 views

Do metals *really* conduct at zero temperature?

The questions is mostly in the title, but might expose another of my misunderstanding of the band structure of solids and how that leads to metals and insulators. If we have a solid, and the fermi ...
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130 views

Why Integer Quantum Hall Effect (IQHE) can only happen in even dimensions?

I read that Integer Quantum Hall Effect (IQHE) can only exist in even dimensions, while Quantum Spin Hall Effect (QSHE) can be generalized to 3D (or rather any dimensions?). Does anyone have a hand-...
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117 views

What's phonon mean free path

This is probably a naive question but still. Phonons are quasiparticles that emerge when we quantize motion of a lattice. In this sense, they have no location in space, they are just energy quanta of ...
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39 views

Can measurement of Spontaneous Magnetization and susceptibility lead one to deduce the magnetic structure of a magnetic compound?

For a given magnetic compound, spontaneous magnetization and susceptibility are measured at various temperatures (in this paper). (SMS measurement) From neutron diffraction data the compound is found ...
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71 views

different energies for the same k vector for free electrons in a solid

when we use the nearly free electron approximations for electrons in a solid and get them as plane waves the energy becomes $E=\frac{\hbar^2k^2}{2m}$, which gives us a parabola. but when we see the ...
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91 views

Why is there a superconducting dome in superconductors?

Generally speaking, by the well-known BCS theory, the more carrier density( density of state at Fermi surface) leads to higher critical temperature. However, in many researches, people fond that the ...
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2k views

Emergent symmetries

As we know, spontaneous symmetry breaking(SSB) is a very important concept in physics. Loosely speaking, zero temprature SSB says that the Hamiltonian of a quantum system has some symmetry, but the ...
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151 views

How can I write the Anderson hamiltonian as a matrix? [closed]

How can I write this Hamiltonian: $$ H = \sum E_d \hat{n}_d + \sum_k \epsilon_k\hat{n}_k + \sum_k V_{kd} (\hat{a}^\dagger_k \hat{a}_d + \hat{a}^\dagger_d \hat{a}_k) $$ in matrix form using its ...
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52 views

Conductance measurement of InAs/GaSb Quantum Spin Hall Edges

My questions are related to recent article: http://arxiv.org/ftp/arxiv/papers/1507/1507.08362.pdf I can't figure out how their sample (wafers) actually looked like. In particular I can't understand ...
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24 views

Why aren't most ionic/covalent/metallic materials self-healing?

For the most part, only soft-matter materials appear to possess self-healing capabilities (that is, if I cleave the material and then press the two halves together, the material re-forms) at room ...
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111 views

Atomic physics - lattice energy

Question: Why is ionic lattice energy inversely proportional to the radius of the atom? Most heterogeneous covalent molecules are polar to some extent. The degree of polarity, or the dipole moment, ...
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39 views

Neutralizing Background and Fractional Quantum Hall ground state

The idealized many-body Hamiltonian describing FQH is given by $$ H = \sum_i \left\{\frac{[\vec{p}_i -e/c \vec{A}(\vec{r}_i)]^2}{2m}+V(\vec{r}_i)\right\} + \frac{1}{2}\sum_{i\neq j} \frac{e^2}{|\vec{r}...
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71 views

Correspondence between variational method and Feynman diagrams

There are two ways to look at the Hartree or Hartree-Fock equations. One method relies on the variational method for a particular type of the probe function and the second one originates from ...
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47 views

Effective mass approximation Wannier function lattice vector operator approximate representation proof. Yu and Cardona

I am having difficulty in Yu and Cardona 4th edition chapter 4 page 164, equation 4.9 to 4.10 I just do not understand how to go from line 4.9 to 4.10. 4.9: $$ R_{op} \psi(\mathbf{r}) = \sum_{n,\...
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826 views

To what extent can the superconducting order parameter be thought of as a macroscopic wavefunction?

I know that the order parameter does not obey the Schrodinger equation; it instead obeys the Ginzburg-Landau equation. However, I am unclear as to the situations under which the view of the ...
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121 views

Number Conserving Superconductors

Usual BCS theory used to describe superconductors violates particle number conservation, this is allowed since that theory is written in a grand canonical ensemble (i.e particles can be exchanges ...
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91 views

Landau level for quadratic band touching in Dirac Hamiltonian

I wonder if there is anyone or any references that have solved the Landau level spectrum and eigenstates with respect to the following Hamiltonian: \begin{equation} H=\frac{k_x^2-k_y^2}{m}\sigma_x+\...