Questions tagged [superfluidity]
A flow with no viscosity
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Spectral function of superconductor in the BEC regime: how does Higgs mechanism affect the spectrum?
Consider the standard BCS theory but assume that the interaction energy $U$ that enters the definition of gap parameter (i.e. $\Delta = (U/N)\sum_k \langle c_{-k\downarrow} c_{k\uparrow} \rangle$, ...
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Superfluid dispersion relation
So I have derived that the action of the superfluid is
$$ S_{\text{eff}} = \int d \tau d^d r \left ( \frac{(\partial_{\tau} \theta)^2}{2g} + \frac{1}{2m} \rho_0 (\nabla \theta)^2 \right ) $$
And we ...
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What is the difference and relation between Hartree-Fock and Hartree-Fock-Bogoliubov?
In nuclear physics literature, both appear very often.
HF is easy. It refers to a variational method with a Slater determinant variational wave function. What is HFB? Does it refer to a similar ...
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A small question about off-diagonal long ranged order
I am studying the off-diagonal long ranged order from the book Superconductivity, Superfluids, and Condensates by James F. Annett. Thereof, I got stuck in a small step from (5.63) to (5.64)(Section 5....
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Hubbard-Stratonovich for 4-component attractive interaction
Suppose we are dealing with a hamiltonian similar to a BCS one, but instead of the 2-component interaction we are dealing with something of the form: $-g\psi^\dagger_1\psi^\dagger_2\psi^\dagger_3\psi^\...
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How does superfluidity not break the conservation of energy?
A superfluid has a property that makes it creep up the walls of its container and escape it until it's empty.
How is it possible that the fluid performs work (against the force of gravity)? I can ...
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Superfluid-Maxwell duality and confinement in 3D
I learned in a class I took that there is a duality between a $D=3$ superfluid and $D=3$ Maxwell theory ($D$ being the dimension of spacetime). In the Euclidean formulation, the action of the ...
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Violation of Lorentz Invariance
Are there any physical systems that violate Lorentz invariance?
When I asked this question from an AI bot I got the following reply:
"Yes, there are physical systems in which Lorentz invariance ...
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Vortices in a Superconductor: triangular lattice VS other geometries
Why do vortices in a superconductor (i.e. magnetic flux-tubes) form triangular lattices? In one of the articles I found, I read that a square lattice would cause repulsion but a triangular lattice ...
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Books on superfluidity in nuclei
can you recommend me some books or other kind of materials to study superfluidity phenomena in atomic nuclei? I'm interested in HFB method as well.\
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Energy of a Bose-Einstein condensate (BEC) in a rotating ring
I was looking at a Bose-Einstein condensate rotating in a ring. Now the energy of the BEC as a function of the angular frequency $\Omega$ is parabolic depending upon the eigenvalue of the angular ...
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Can you burn a quantum fluid?
Perhaps more generally, can you have a chemical reaction between a quantum fluid (a sodium Bose-Einstein condensate for example) and another quantum fluid or a non-quantum fluid?
Or as a silly ...
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Buoyant force in a tub filled with multicolour balls
Would there be a buoyant force on a moving object like a human in a multicoloured balls(say 1cm diameter) filled tub? Or would it be like a superfluid, so that the human would sink right in without ...
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A pendulum in a superfluid
Imagine to submerge a pendulum in a supefluid. Of course we assume an ideal pendulum, whose joint does not freeze or deteriorate due to the extremely low temperature. We also assume the superfluid to ...
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Why doesn't Superfluid Circulation Vanish?
In superfluid, the hydrodynamic velocity, $v$, is proportional to the gradient of the wavefunction phase: $\vec v= \frac \hbar m \nabla \phi$.
Given that, the circulation along a closed path, that ...
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Superfludity and Superconductivity
Hello Im a physics enthusiast, right now im learning about superfluidity. My question is superfluidity and superconductivity are the same thing or do they work together?
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How to properly get low energy effective field theory of superfluid?
I am following chapter 3 of X. G. Wen's book "Quantum Field Theory of Many-Body Systems". The following action for a weakly interacting Bose gas is derived:
$$S[\varphi,\varphi^*] = \int dt \...
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Why do superfluids even climb walls?
The question I have been puzzling over is how can superfluids climb walls?
I know there is a force that overcomes gravity. I thought perhaps the van de Waals force is so weak between superfluid atoms ...
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Do the quantum vortices defects generated in a rotating superfluid have higher temperature than the rest of the bulk of the superfluid?
Do these defects actually correspond in a local acceleration of the superfluid or deceleration?
And if superfluid is locally accelerated inside these vortices wouldn't that rise the temperature of the ...
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Why Superfluid Vacuum Theory has not proved yet that Vacuum space is possible a superfluid?
Our Universe and subatomic world being defects of an omnipresent type of superfluid we call "Vacuum Space" therefore a medium, unknown phase of matter is an intriguing idea expressed by SVT.
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How the concept of "wave function of atom" in Bose-Einstein condensate should be interpreted from perspective of quantum field theory?
A typical description of Bose-Einstein condensate goes along the line of "multiple atoms in the same ground state can be described by the same wave function". But hold on. Atoms are not ...
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Excitations of Neutral Superfluids and their Interactions
I need some clarifications about the low energy excitations superfluids and their interactions.
First case, Bose superfluid: As far as I know, there are 3 kinds of commonly known excitations in this ...
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Fluid in a Rotating Cube
Fluid in a rotating cylinder has a paraboloid shape. But, I was wondering what shape would the liquid take in a rotating cube. If possible, explain mathematically.
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Cryogenic Particle Detectors
Recently, I started reading about Neutrinos, their types, oscillations and their detection.
Today many experiments are being conducted to detect and measure oscillations of sterile neutrinos and anti-...
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Do inviscid fluids have thermal conductivity?
Inviscid fluids are an idealization and they don't have viscosity. The no-slip boundary condition DOESN'T apply to them and consequently, these fluids won't display a hydrodynamic boundary layer.
I've ...
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What role do quantized vortices play from the Superfluid model in Superfluid Vacuum Theory?
When rotating a superfluid (such as $^{4}$He) below its critical temperature, sometimes quantized vortices pop up, depending how fast one rotates this superfluid. In the SVT model, they propose that ...
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How does all of the superfluid empty from the beaker?
From what I understand, a superfluid is comprised of its normal fluid component and superfluid component (Landau's two fluid model). This normal fluid component has viscosity. What I don't understand, ...
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Why do "quantum vortices" form in superfluids?
I've been reading up on Superfluids, and they've fascinated me. I understand why their superfluid component has zero viscosity, but there's one aspect that's bothering me, and that's the formation of ...
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Qualitative difference of excitations in Fermi VS Bose superfluids
Assume that we have an electrically neutral interacting gas (or liquid) of Bose or Fermi particles in a superfluid state.
For simplicity, assume that the particles interact via an assigned central ...
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Connection between superfluid density and spin stiffness
I am currently trying to understand the apparent equivalence between spin stiffness and superfluid density. I (think I) understand how the XXZ model maps onto the Boson-Hubbard model with the ...
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Nambu-Goldstone mode without symmetry breaking
Superfluidity is often explained in terms of spontaneous breaking of global $U(1)$ symmetry. However, we know that in real, finite-size quantum systems, this symmetry can never be broken. Quantum ...
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Capillary action in presence of weight and atmospheric pressure
In capillary action the water for example rises in a small-diameter-glass tube due to that the cohesive and adhesive forces are larger than gravity and fall if they were less than gravity .The ...
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Double slit experiment on superfluid surface. What do we observe?
What do we observe when we perform a double slit experiment with mechanical waves on the surface of a superfluid?
Do the ripples on the superfluid form and propagate similar to ones on water? What ...
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Will the water level keep rising up after attaining terminal velocity?
Suppose I have an infinitely long container of water and I dropped a metal ball into it.
Initially, the water level will rise up due to displacement of volume. But will it keep rising when the whole ...
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Connection between superfluidity and temperature
I don't understand the significance of temperature in relation to the presence of superfluidity. Why, in general, are low temperatures necessary?
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Is a vortex crystal a supersolid?
Reading the article [Rev. Mod. Phys. 84, 759 (2012)] by Prokof'ev and Boninsegni, a supersolid is defined as a homogeneous phase of matter in which both density long-range order (i.e. ordered spatial ...
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How $^3\text{He}$ atoms remove thermal energy from surrounding environment in dilution refrigerator?
I am trying to understand how a dilution refrigerator works.
I understand that $^3\text{He}$ atoms are pumped out of the diluted phase and to reestablish an equilibrium, new $^3\text{He}$ move there ...
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Difference between BEC and Superfluidity. Why is considered superfluid helium not a BEC?
I have not a clear idea what the difference between a BEC of weakly interacting bosons and superfluid is. My second question that could help me understand this difference is: why do alkali atoms form ...
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Does superfluid have substructure? I mean does the substructure matter?
My main research interest is the gravitational wave. Recently, I and my academic brother watched a famous video about the superfluid. I read a review then came up with some questions.
Here is the ...
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Quantum vs Classical Vorticities
Excepting the circulation quantization, what are the differences between classical vorticities (created in classical fluids) and quantum vorticities (BEC superfluids)?
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How does particle-particle interactions affect superfluids?
Ive read that London approach of superfluidity was wrong because he took them as non-interacting bose gas molecules and got incorrect temperature dependence for density, but also one can take ...
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Problems met in Matsubara frequency sum
I would like to calculate $\sum\limits_{\omega_{n},\vec{k}}(\ln(-i\omega_{n}+\xi_{\vec{k}})+\ln(-i\omega_{n}-\xi_{\vec{k}}))$, where $\omega_{n}=\frac{(2n+1)\pi}{\beta}$ and $n=0,\pm1,\pm2,\dots$
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Matsubara sum in mean field theory of superfluid
Ths system is given in Doppler shift in current-carrying superfluid. Here to make mean-field theory, we set $\vec{Q}=0$ and $\Delta(x)=\Delta_{0}$.
After some manipulations, we obtain the ...
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Superfluid + Super conductivity in a bose condensate
so my question is this
can we theoretically and empirically find a BOSE condensate, with SUPERFLUID properties but which is also
a SUPERCONDUCTING device ?
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Why the electric field inside a superconductor is always zero?
Recently I have been reading the book called "Superconductivity, Superfluids and Condensates" from James F. Annett. I was confused by the expression that
zero electric field at all points ...
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Superfluid condensate wave function
I am reading Girvin's Modern Condensed Matter Physics and I have a question about the off-diagonal long-range order (ODLRO). In chapter 18.1, he starts from
\begin{align}
\rho(\vec{r},\vec{r}') = \...
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Lagrangian for a fixed number of non-interacting, non-relativistic bosons
In my book on QFT, (during an explanation of superfluidity) the author states that the lagrangian for a fixed number of non-interacting, non-relativistic bosons is $$i\Phi^{\dagger}\partial _{0}\Phi-\...
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Ginzburg-Landau and Coherence Length
Consider the Ginzburg-Landau functional for a complex function $\psi:\mathbb{R}^3 \to \mathbb{C}$, i.e.,
$$
F[\psi]=\int \frac{1}{2M}|(-i\hbar\nabla -eA)\psi|^2+r|\psi|^2+\frac{u}{2}|\psi|^4 + \frac{B^...
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Ground state of composite and non-interacting bosons on a lattice
Background
Consider a lattice system described by the Hamiltonian
$$
H = - J \sum_{\left\langle ij \right\rangle} \left( \Delta^{\dagger}_i \Delta_j + \mathrm{h.c.} \right)
$$
where $\Delta_i$, $\...
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Conceptual doubt in Superfluidity
I'm trying to understand superfluidity from these Caltech notes on Advanced Statistical Physics (Week 1, Section IV: Landau Criterion for Superfluidity) -
So far it is not clear why a moving ...
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