# Tag Info

### 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 ...
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### 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 ...
Accepted

### 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 ...
• 50.9k
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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 ...
• 187
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### Are superinsulators perfect dielectrics?

Yes. Just as superconductors truly are perfect conductors, superinsulators truly are perfect dielectrics. In the bulk, they have zero permittivity. As such, this gives rise to the complete expulsion ...
• 3,819
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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, \...
Accepted

### 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 ...
• 32.9k
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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 ...
• 960
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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 ...
• 187
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-...
• 960
1 vote
Accepted

• 3,819
1 vote
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### Which experiments can offer insights about Hubbard $U$ parameter?

When considering $\mathrm{DFT}+U$ calculations, people either go with (1) first-principles approach: calculating the $U$ parameter using linear response theory, $\mathrm{DFPT}$, $\mathrm{ACBN0}$, etc.,...
• 21.8k
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....
• 21.8k

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