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

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Property of helium superfluid [on hold]

I learnt that in helium II every atom would have same wave function and is governed by BE statistics. does that mean all helium II atoms would vibrate in the same way in a field?
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34 views

Can we say an atom is ferromagnetic?

Some atoms have nonzero magnetic moments. Does it make sense to say they are ferromagnetic? Or should we say it is paramagnetic?
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46 views

Anomaly for Majorana fermion?

In 4-spacetime dimension, is there U(1) gauge field chiral anomaly associated with Majorana fermion (or I am not sure if it is equivalent, majorana representation)? Besides, I have read from several ...
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65 views

effective field theory of the projective semion model

The "projective semion" model was considered in http://arxiv.org/abs/1403.6491 (page 2). It is a symmetry enriched topological (SET) phase. There is one non-trivial anyon, a semion $s$ which induces a ...
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31 views

what is the difference between the trivial SPT phase and nontrivial SPT phase?

I read some paper and found two terms "trivial SPT" and "nontrivial SPT". I am wondering what is the difference between trivial SPT and nontrivial SPT. Thank you! SPT stands for symmetry-protected ...
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12 views

Effect of applying a gate voltage to a strongly correlated system

In strongly correlated systems, there are different ways of driving a metal-insulator transition (MIT), say, bandwidth control, filling control and dimensionality control (See MIT). As for the method ...
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How can I calculate the character table for double group in spin-orbit interaction

When I read the book(Group theory: application to condensed matter physics) page 347, I found I don't know how to derive the new irreducible representations in the double group.
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15 views

Density of energy eigenstates in Heisenberg model

Consider the Heisenberg model for spin-$\frac{1}{2}$ particles in 1 dimension. Take the case described by the hamiltonian: $J\sum_{i,i+1}(\sigma^x_i\sigma^x_{i+1} + \sigma^y_i\sigma^y_{i+1} + ...
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1answer
42 views

Confusion between band structure and energy gap of conventional superconductor

Can anyone please clarify my confusion? Why does a superconducting state conducts electricity even if it has an energy gap? The difference between metals and insulators is that there is a gap at the ...
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64 views

Precisely speaking, does photon become massive or the phonon become massive, due to Higgs mechanism in superconductor?

Consider the low energy field theory of both superfluid and superdonductors. In superfluid, the spontaneously breaking of the phase of the order parameter lead to the creation of the massless ...
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2answers
40 views

Phonon spectrum

I had a question regarding phonon spectrum in condensed matter. Consider a cubic lattice with '$p$' atoms per primitive cell. Consider the lattice plane used for derivation of the phonon spectrum to ...
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80 views

How is the current equation calculated from Ginzburg-Landau (GL) free energy?

In the Ginzburg-Landau theory, we can get the current expression from GL free energy: $$F = \int dV \left \{\alpha |\psi|^2 + \frac{\beta}{2}|\psi|^4 + \frac{1}{2m^*} \mid (\frac{\hbar}{i}\nabla - ...
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177 views

A naive question about topologically ordered wavefunction?

Topological entanglement entropy (TEE, proposed by Levin, Wen, Kitaev, and Preskill) is a direct characterization of the topological order encoded in a wavefunction. Here I have some confusions, and ...
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2answers
29 views

What is the physical significance of the Curie constant?

What is the physical significance of the Curie constant? I understand it depends on the effective moment of the ion and hence must be some measure of it, but what is it exactly? Like some average ...
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2answers
27 views

Is there any relation between temperature dependence of resistance and fermi energy in metals?

Given that the resistance varies linearly with temperature in metals, is there any way we can calculate the Fermi energy from this information?
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20 views

What is the spin of a magnetic impurity?

I am reading this seemingly important paper Local Magnetic Moment Associated with an Iron Atom Dissolved in Various Transition Metal Alloys. It is strange to me that the magnetic impurity has ...
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1answer
34 views

Dielectric constant of Transition Metal Dichalcogenides (TMD)

Why is the in-plane dielectric constant of transition metal dichalcogenides larger than the out-of-plane dielectric constant? Is this because of the spacing between monolayers of the TMD? Why do ...
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40 views

Can a conformal field theory with chiral central charge be gapped out?

Consider a 2-dimensional conformal field theory with nonzero chiral central charge (that is, the central charges of the holomorphic and antiholomorphic sectors are different.) I think that ...
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2answers
124 views

What makes a superconductor topological?

I have read a fair bit about topological insulators and proximity induced Majorana bound states when placing a superconductor in proximity to a topological insulator. I've also read a bit about ...
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24 views

Normal modes and lattice symmetry

In chapter 22 of Ashcroft & Mermin, it says: Theorem: any transformation that leaves $\mathbf{k}$ and the lattice invariant must transform one normal mode with wave-vector $\mathbf{k}$ to ...
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2answers
99 views

Why do objects have size? [closed]

What is the reason objects, like coffee mugs, have size?
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53 views

why doesn't liquid metal vaporize in a vacuum?

I am wondering why molten metal in a vacuum of electron beam and machines never turns to gas like liquid water does when exposed to a vacuum.
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21 views

ZnO nanorods synthesis

Could someone please let me know the steps to be used for sol-gel method synthesis of ZnO nanorod arrays using PVA as solvent and Zn acetate as precursor? I need vertical and uniformly aligned NR ...
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21 views

Debye-Huekel Theory and the continuum approximation

This question stems from a problem I was doing on the Debye-Hueckel theory. It says that the continuum approximation which underlies the Debye-Hueckel theory is valid provided that $\lambda_D \gg ...
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62 views

Equivalence classes of mappings from $T^{2}$ to an arbitrary space $X$

I was reading the paper "Homotopy and quantization in condensed matter physics", by J.E Avron et al. ( http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.51.51). There they have classified the ...
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72 views

Phase Transition at Zero Temperature (Not QPT)

As is well known the Ising model exhibits a phase transition, except the one dimensional case in which the phase transition occurs strictly at $T=0$. Now I have always thought that this makes the case ...
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46 views

How do i correctly go from a two variable function to a function of difference? [migrated]

I would like to know how I can go from a two argument function $g(x_1,x_2)$ formally correct to a function of the difference of the parameters $g(x_1-x_2)=g(x)$ this seems to involve integration over ...
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66 views

Relation between scattering matrix and an effective Hamiltonian

Could somebody provide the proof (or reference to some accessible literature) of relation $$S(E) = 1 + 2πiW^{†} (H_M − E − iπW W^{†} )^{−1} W \tag{2}$$ of arXiv:0806.4889, which relates $S$-matrix to ...
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1answer
81 views

Hartree Fock equations

I don't understand how the Hartree Fock equations define an iterative method! For this discussion, I am referring to the HF equations as described here: click me! Basically if you guess a bunch of ...
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19 views

How to calculate phonon decay rate?

Here, the authors calculate the quality factor for a resonator. They take it as one over phonon decay rate, given by (24). Simplified, (24) looks like this: \begin{equation} \Gamma = \gamma_{N-1,N} - ...
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Is it possible to write the Lorentz oscillator model using Green's functions concepts?

Is it possible to write: $$\lim_{\gamma_j\rightarrow0}Im\left(\frac{1}{\omega_j^2 - \omega^2 - i\omega \gamma_j}\right)$$ which occurs, for example, in the Drude-Lorentz oscillator model for ...
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1answer
102 views

What does a correlation function measure and how does it do this mathematically?

I would really appreciate if someone could explain. What does a correlation function like a density-density correlation function $$C_{nn}(\vec x_1, \vec x_2)= \langle n(\vec x_1) n(\vec x_2)\rangle$$ ...
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33 views

How to derive De Haas–van Alphen effect?

I was reading Solid State Physics by Kittel and they manage to derive De Haas–van Alphen effect by invoking the Bohr-Sommerfeld model. This feels unsatisfactory to me. Can someone derive this using ...
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43 views

Tight binding in the limit of large system size

Suppose that one has a continuous Hamiltonian with spin-orbit interaction, for example $H=-\dfrac{\mathbf{p}^2}{2m} +\kappa({\boldsymbol\sigma}\times\mathbf{p}) + U(x)$ and want to approximate this ...
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What kinds of behavioural anomalies can a zero-field-cooled (ZFC) / field-cooled (FC) split indicate?

If a material shows a spiltting in the ZFC and FC curves, is it necessarily superparamagnetic, or could there be any other reason for the irreversibility? I have heard spin glasses also show ZFC-FC ...
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47 views

Time evolution of a discrete 1-d lattice of spin-(1/2) particles under a given Hamiltonian, or special cases thereof

I am trying to get some feel for the dynamics induced on a discrete 1-d lattice of spin-(1/2) quantum particles by the following Hamiltonian $\hat{H} = \sum_{i, j} r_{i j} \left[ ...
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How are topological invariants constructed?

I've seen several different definitions for what are called topological invariants, for instance in the context of Majorana unpaired modes, by Kitaev: http://arxiv.org/abs/cond-mat/0010440 ...
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Defining a gauge field for an anisotropic material under strain

I have a Hamiltonian for a system which is somewhat analogous to graphene but with additional degrees of freedom. The Hamiltonian is $H=\sum_q \Psi^\dagger \mathcal{H}\Psi$ where ...
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47 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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1answer
34 views

Coulomb repulsion in the Anderson impurity model

In Phil Anderson's famous paper on impurities, Localized Magnetic States in Metals, he has the following paragraph on page 44, However, I am puzzled by the last sentence: why is the $J$ part ...
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1answer
77 views

How to obtain the asymptotic behavior of Green's function?

This question arose from Eq.(9.135) and Eq.(9.136) in Fradkin's Field theories of condensed matter physics (2nd Ed.). The author mapped quantum-dimer models to an action of monopole gas in $(2+1)$ ...
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89 views

Below what temperature does a semiconductor stop behaving intrinsically?

I understand that for an intrinsic semiconductor $n=p$ where $n$ is the electron carrier concentration and $p$ is the hole concentration.My question is how to calculate the temperature at which the ...
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91 views

What exactly happens at the second-order phase transition of the 2D Toric code?

For a 2D Toric code specified by $$H = -J_s\sum_{s} \prod_{j\in s} \sigma^x_j - J_p\sum_{p} \prod_{j\in p} \sigma^z_p - h_x\sum_{l} \sigma^x_l - h_z\sum_{l} \sigma^z_l$$ where $s$ denotes stars, $p$ ...
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1answer
86 views

Contructive Proof of 2nd Quantization form of Operators

Is there a constructive proof for these forms of operators in second quantization $$R= \sum \limits_a \sum \limits_b \langle a | R_1 | b \rangle C_a^\dagger C_b $$ using the general form $R = \sum ...
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3answers
51 views

How to find dielectric constants of ferroelectric materials experimentally?

What is the procedure to find out dielectric constant of barium titanate at different temperatures ?
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24 views

How to understand the Bose glass phase has infinite superfluid susceptibility?

The Bose glass phase is characterized by a gapless excitation spectrum, exponential decay of superfluid correlations, finite compressibility and infinite superfluid susceptibility. The disordered ...
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71 views

How is the average particle density defined in condensed matter physics?

I am reading a script where average density is defined as: $n(\vec x) = \langle \hat \rho(\vec x) \rangle = \langle {\hat \Psi^\dagger(\vec x)} \hat \Psi(\vec x) \rangle$ which i absolutely don't ...
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46 views

Electron-Hole Spin Exchange Interaction

I am stuck with this seemingly "simple" Hamiltonian. I am dealing with an exchange term of a Hamiltonian for two different spin species: $$H_\text{exchange} = - \lambda J \cdot S = ...
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1answer
47 views

Eigenvalues of a nearest-neighbour tight-binding Hamiltonian in (Mahan, 2003)

In this paper by G. D. Mahan, he obtains the following electron Hamiltonian in a nearest-neighbour tight binding scheme: (page 2 of the paper, top of the right column) \begin{align} H_0 &= J_0 ...
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Surface Plasmon-Polaritons in magnetic media

It's easy to calculate the dispersion relation for SPPs present in a vacuum-nonmagnetic metal interface. (See here) What about ferromagnetic metals? How can one calculate the dispersion relation of ...