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1D Lattice with site dependent magnetic field

I would say the result is just a statement about the structure of the phase/configuration space, which is spherical with no preferred direction(s) in the case of a magnetic moment. The partition ...
Crisco's user avatar
  • 95
0 votes

Non-crossing approximation (NCA) in 'Large-$N$ expansion' (Altland & Simons CMFT)

Let me just write down a proper answer. I will address the questions in reverse order. The wavy line is a notational device that splits the four-point vertex into two sides. Given the interaction $$ ...
T.P. Ho's user avatar
  • 91
8 votes
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Jellium Hamiltonian in the thermodynamic limit

To quote the standard reference on the Jellium:$^1$ The physical hamiltonian is recovered by letting $\kappa \to 0$ after going to the thermodynamic limit $L\to \infty$. The procedure is justified a ...
Tobias Fünke's user avatar
1 vote

Has Chandra Varma explained cuprate superconductivity?

An update on this old question: Recently, an independent group has analyzed the possibility of Cooper pairing driven by loop current fluctuations in Sci. Adv. 10, eadn3662 (2024). In contrast to an ...
user414739's user avatar
1 vote
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DMRG for anyons

I did some tests using ITensor and decided to answer my own question. Yes, embedding the anyonic degrees of freedom into spin degrees of freedom does seem to work (at least it appears to from the ...
Souroy's user avatar
  • 193
0 votes
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Mahan's derivation of energy current of a free-particle system

TLDR: $\textbf{r}\mathcal{H}$ is $\textbf{r}\psi^* H\psi$. In more detail, this is really several questions in a trench coat. First of all, Q: What does the energy current actually represent? If we ...
Redcrazyguy's user avatar
2 votes
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Finding the classical antiferromagnetic ground state for the Kagomé lattice

The full exercise is: Employing only symmetry considerations, identify a possible classical ground state of the triangular lattice Heisenberg antiferromagnet. (Hint: construct the classical ground ...
Rokas Veitas's user avatar
2 votes
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$p+ip$ pairing in a spinless fermion system with attractive interaction

A spinless fermion system with attractive interactions supports p+ip pairing. In a spinless fermion system, there is no spin degree of freedom, which means the pairing must occur purely in the ...
Adam's user avatar
  • 187
0 votes

Is magneto-optic Kerr effect discernible for material with natural optical activity?

From an experimentalist's point of view: If the material's chiral structure is independent of the external field or magnetism, then the sample's optical activity will be calibrated out of the result ...
ABetheGammow's user avatar
1 vote
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Bloch oscillations and umklapp scattering induced by applied electric field

An Umklapp process is any scattering event where the ingoing and outgoing momenta differ by a (nonzero) reciprocal lattice vector. This includes phonon-phonon, but also electron-phonon and electron-...
Rokas Veitas's user avatar
1 vote
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Permittivity real and imaginary parts with similar value possible?

Since the right side of the second figure is not clear because of the inappropriate scale, I will only analyze the left half of the frequency range. Obviously, the imaginary part of the permittivity $\...
et al.'s user avatar
  • 151
4 votes

Other than approximating the total energy of the system, what other information does the Hartree-Fock method provide?

In addition to energy, Hartree-Fock gives you the optimal wave function of the many-electron system (within the limits of the theory) as well. Any physical observable can be obtained from the wave ...
Perttu Hilla's user avatar
2 votes
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Using particle-hole symmetry of the Hubbard model to study the model at different densities

$\newcommand{\dag}{\dagger}$I realized it's because there are two spins that must be accounted for. Under the particle-hole transformation, we have \begin{align*} N = \sum_{i, \sigma} a^\dag_{i, \...
zeroknowledgeprover's user avatar
0 votes
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How do you get from the polarisation operator to particle current?

The confusion arises from how Mahan's notation. Writing the polarisation operator w.r.t. the basis vectors $e_i$ $$\textbf{P}=\sum\left(\int x^i\rho(\textbf{r})d^3r\right)e_i$$ Since $\partial_t\rho$'...
Redcrazyguy's user avatar
3 votes
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Derivation of two-body Coulomb interaction in momentum space

This is not possible to answer without knowing all of your source's relevant conventions, including the Fourier transform. One way you can check the book is look for a place where they use this ...
Andrew's user avatar
  • 51.2k
5 votes

Solid-on-solid models

First, I'd say that the case you describe corresponds to a wetting transition, rather than to a roughening transition: the system goes from a regime of complete wetting (the wall if fully covered by a ...
Yvan Velenik's user avatar
  • 10.5k
1 vote

Why can't bosonic systems have fermionic excitations?

When reading Abrikosov's book AGD, there is a statement that 'It is obvious only that a Bose system can not have excitations with half-integral spins' (page 5). I don't understand why this is the case....
hft's user avatar
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2 votes
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Could there be states of matter that could avoid "matter decay"?

Baryon decay can be avoided if you build something out of stable non-baryonic matter. Given our currently known particles that leaves electrons/positrons, and neutrinos. Stable electron clouds are ...
Anders Sandberg's user avatar
0 votes

Why surface and bulk states of topological insulators (TI) have different topological invariants and how it leads to conductive states?

In the standard sense, when we think about topological classification/topological order - we think of dividing ground states of local and gapped Hamiltonians (with the symmetry eigenvalue if we are ...
Adam's user avatar
  • 187
3 votes
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What is the Haldane gap?

Short answer: Haldane Gap is just a name for a gap in the band structure occurring at the K and K' points for the Haldane model. It tells us which sector of the phase diagram we are in and what ...
Adam's user avatar
  • 187

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