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The study of physical properties of condensed phases of matter, including solids and liquids.
285 questions from the last 365 days
4
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answers
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Do we have good general models for solid-liquid phase transitions?
When reading about phase transitions, one quickly encounters the Ising model and its variants (spin glass, Potts, etc.).
This model is used to explain ferromagnetism in a very satisfying way. It is ...
- 354
0
votes
0
answers
46
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DFT Calculation with spin-orbit coupling (SOC) turned off but Magnetization turned On [closed]
I'm having trouble obtaining accurate band structure calculations with spin-orbit coupling (SOC) turned off while magnetization is turned on. When SOC is enabled, the results are accurate and ...
- 1
-3
votes
0
answers
55
views
Masters course recommendations in Spain or Italy [closed]
I am completing the final year of my bachelors next academic year in Trinity College Dublin in Theoretical Physics, which is a 4 year course which contains courses on QFT, the Standard Model, ...
2
votes
1
answer
165
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Semiclassical electron dynamics and Pauli exclusion principle
I believe a similar question is asked here, but there doesn't seem to be a satisfactory answer so I'd like to reformulate it.
In the semiclassical model of electron transport, electrons are described ...
1
vote
1
answer
77
views
How to derive the equation of motion for the field operator in an interacting fermion system?
I am trying to derive the equation of motion for the field operator in an interacting fermionic system, starting from the second-quantized Hamiltonian:
\begin{equation}
H =\int d r \psi_\gamma^{\...
- 81
1
vote
0
answers
45
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Is plastic deformation a form of hysteresis?
I am currently studying materials sciences, and I have just come across the concept of "stress-strain curve". As I understand it, as long as we keep the material in its elastic region, we ...
- 2,266
0
votes
0
answers
20
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Could unconventional superconductivity breaks generalized symmetry?
I am currently a student learning about superconductivity. I understand that conventional superconductivity breaks U(1) gauge symmetry, while unconventional superconductivity breaks additional ...
- 1
2
votes
0
answers
33
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Unitary mixing of degenerate eigenvectors in numerics causing issues with anamolous spectral function
I am working on solving a Bogoliubov-deGennes (BdG) Hamiltonian, but I am running into an issue when calculating the anomalous Green function: there is a phase ambiguity between degenerate or nearly ...
- 499
3
votes
2
answers
196
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Analogy of X-ray edge singularity problem for longer wavelength
X-ray edge singularity means that when one uses X-ray to excite the core electron, one will see that the absorption cross-section exhibits a power-law divergence at a certain frequency threshold above ...
- 668
0
votes
0
answers
37
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Different roots in dispersion relation
I am looking at the dispersion relation of my system at different temperatures, solving the pole of the determinant of the Gaussian fluctuations matrix
$$
\begin{align}
\frac{1}{2}\sum_q\left(\hat{\...
- 475
1
vote
0
answers
21
views
Point group or Space group symmetry on Berry connection [closed]
I want to consider How Berry connection transform by Point group or Space group symmetry and whether is it possible to think selection rule as other quantity.
For <n|O|m> term, we usually ...
- 11
2
votes
1
answer
42
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Are there really zero Cooper pairs in the ground state of the Cooper Pair Box?
Trying to get an understanding of superconducting charge qubits. The literature I've read seems to indicate that the energy levels of the qubit correspond to the number of Cooper pairs on the ...
- 151
0
votes
0
answers
23
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Non-local interactions in Hubbard model - form factor of pairing operators
Context
I am studying the Extended Hubbard Model with NN attraction at half-filling,
$$
\hat H = -t
\sum_{\langle ij \rangle} \sum_\sigma \hat c_{i\sigma}^\dagger \hat c_{j\sigma}
+ U \sum_i \hat n_{i\...
- 21
1
vote
0
answers
38
views
Computing the particle-hole (polarization) bubble in a system with anisotropic dispersion
I am trying to calculate the particle-hole bubble in 2D space in the presence of a Van Hove singularity whose local dispersion is of the form
$$\varepsilon_k = \frac{|t|}{4} k^3 cos(3\theta_k)$$
and ...
- 11
2
votes
1
answer
39
views
Choosing a suitable representation of the Hubbard interaction
There are several ways to define interaction term in the Hubbard model.
The standard one for most people is probably \begin{equation}
U\sum_in_i^\uparrow n_i^\downarrow.
\end{equation}
Then there are ...
- 33