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Questions tagged [superfluidity]

A flow with no viscosity

48 questions with no upvoted or accepted answers
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12
votes
1answer
350 views

Why are superfluid vortex lattices stable?

Both (a) neutral superfluids that are externally rotated, and (b) type-II superconductors (i.e. charged superfluids) under applied magnetic fields between the critical fields $h_{c1}$ and $h_{c2}$, ...
5
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0answers
264 views

Third-order topological quantum phase transition in p+ip superfluid

A two-dimensional spinless non-relativistic p+ip superfluid undergoes a quantum phase transition between the BCS (weakly-coupled) and BEC (strongly-coupled) regimes. This transition is driven by ...
3
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1answer
84 views

Charge-Vortex Duality for Bosons

Consider a (2+1)d continuum field theory with the Minkowski action $$\mathcal{L}=|\partial\phi|^2-r|\phi|^2-u|\phi|^4,$$ where $\phi$ is a complex field. The theory undergoes a quantum phase ...
3
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0answers
197 views

Superfluidity book recommendation

I'm preparing for a senior undergrad seminar on superfluidity and quantized vortices, and my professor seems to prefer old textbooks, so I wondered what modern (~90's onwards) books on these phenomena ...
3
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1answer
236 views

Adiabatic transition from superfluid to Mott insulator?

I have a question about the dynamical passage from superfluid to Mott insulator state in the Bose-Hubbard model. Is it possible to go from superfluid region to the Mott insulator by changing the ...
3
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0answers
40 views

Can we 'dope' a fluid to make it become a superfluid?

The only element that can become a superfluid is Helium (He-3 and He-4) since it does not solidify not matter how cold it gets, hence it can reach the superfluid transition temperature whilst still a ...
3
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0answers
290 views

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

Consider the low-energy field theories of superfluids and superconductors. In superfluids, the spontaneous breaking of the order parameter's phase creates phonons as the massless Goldstone bosons.(...
3
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0answers
117 views

How can we see that there is superconductivity/superfluidity in the boundary theory in the holographic principle?

For example in the models for holographic superconductors we can calculate the conductivity. Also there is an energy gap. I can understand that it describes a superconductor. However I have also heard ...
2
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0answers
38 views

Do Goldstone modes with linear dispersion always correspond to superfluidity?

For a superfluid, we get that the Goldstone modes has a linear dispersion. $\omega=vk$ where $v$ will be a critical velocity. We can have no excitations caused by impurities with a velocity less that ...
2
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0answers
64 views

Energy dissipation from a black hole by neutrinos

Could the high gravitation field of a black hole cause neutrinos to form a Fermi gas or superfluid? Could these neutrinos from the neutrino background of the big bang whose temperature and deBroglie ...
2
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0answers
59 views

Definition of Superfluid with no Bose-Einstein condensation?

A BEC with no superfluidity is referred to as Bose Glass (due to S. Yukalov to my knowledge). Is anyone aware of a similar definition for systems which exhibit superfluid behaviour but are not Bose-...
2
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0answers
56 views

Observational evidence for superfluidity in neutron stars

What is the earliest evidence for the existence of superfluidity in neutron stars? I'm about to present the subject in a seminar and I'm under the impression that at the moment there is no ...
2
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0answers
176 views

Is gapless spectrum necessary for superfluity

In 3D interacting Boson system, the condensate leads to a gapless spectrum and superfluidity. The same gapless spectrum for 2D with quasi-condensate (correct me if it is wrong ). I am wondering if it ...
2
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0answers
170 views

The appearance of a gapless phase mode in Landau Ginzburg theory of charged superconductor

My question is simply: Why do the Landau Ginzburg(LG) theory of superconductors describe a phase mode which is ungapped/massless when it should be promoted to the plasma frequency? I will try to ...
2
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0answers
117 views

What's the role of BEC in superfluidity?

I'm writing about superfluid $^4$He. I've seen in some places that the transition to superfluid is attributed to Bose-Einstein condensation, but then in others that this model needs a massive amount ...
2
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0answers
230 views

order of BKT phase transition

What is the order of the BKT phase transition (first or second), that is the phase transition in 2d in which thermal vortices destroy any order in the system. How is this connected to the "universal ...
2
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0answers
94 views

Superconductivity and superfluidity energy dissipation

All articles say that in superconductive state, the materials have exactly zero resistance, but is this the case in real life experiment?, because if this were true, a process without energy ...
2
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0answers
89 views

Why are quantum vortices so large?

Quantum vortices in helium are almost macroscopic, and can be be imaged in a light microscope: http://www.aps.org/units/dfd/pressroom/papers/gaff09.cfm How can vorticity be quantized on such a large ...
2
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0answers
102 views

Statistical field theories on topological defects

Systems like superconductors and superfluids are often treated by specifying some phenomenological mean field theory where the free energy is given as a functional of some order parameter field. Given ...
1
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0answers
21 views

Superfluid Vortex Lines Bifurcation and Winding Numbers

Vortex lines in superfluids are characterized by their quantised circulation: $k = \frac{h}{m}\times n$, where $n$ is the winding number in the sense of a topological winding number. Now, most vortex ...
1
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0answers
10 views

Is the streaming of a superliquid through a circular tube equivalent to the current running in a circular piece of superconducting material?

When a superfluid streams endlessly through an isolated circular tube is the same mechanism at work as in the endless current moving through an isolated circular piece of superconducting material? Is ...
1
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0answers
17 views

How will a rotating, circular, and cylindrical body of a superfluid develop in outer space?

Let's consider a rotating (about its center, in the plane cutting the initial circular and cylindrical form into two halves), circular, and cylindrical body of a superfluid somewhere in outer space. ...
1
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0answers
24 views

What would happen if we test the Hagen-Poiseuille law with a superfluid?

When we have a laminar flow we can test the Hagen-Poiseuille law from the pressure difference created by the flow of the fluid. This process is created due to conservation of total energy but the ...
1
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0answers
86 views

What macroscopic fields exist around color supercurrent?

For an ordinary superconductor such as Lead, charge supercurrent gives rise to a magnetic field around the whole material for low enough currents. At large enough currents, the superconductor will ...
1
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0answers
35 views

What is the link between superfluids and BEC?

i’m studying superfluids (in particular $^4 He$) and one of the first theorical apporoach was with Bose-Einstein condensation and i know that we can calculate the $T_c$ and it is close to the the ...
1
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0answers
18 views

Why the form factors on the green function of relativistic two-component liquid model for superfluid have this form?

I am working in trying to understand Appendix A of arXiv:0906.4810. On this appendix, the authors set up an external velocity field perturbating a superfluid, described by a two-component model. This ...
1
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0answers
31 views

Topological properties of dark solitons in superfluid systems

In the study of superfluid systems, vortices are often referred to as "topological excitations", because the winding of the phase of the superfluid order parameter around a vortex is a topological ...
1
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0answers
37 views

The correct expression for pressure, temperature in Landau's 2-fluid model

Setup: the system of equations I would like to numerically solve the equations of motion in Landau's [Ref (1)] two-fluid description of superfluid He II, which are $$ \frac{\partial \rho}{\partial t}...
1
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0answers
273 views

Sod shock tube - Contact Discontinuity

sorry for bothering with my question. https://en.wikipedia.org/wiki/Sod_shock_tube I have trying to understand, how is it possible to have a discontinuity on Density and not on Pressure. I don't ...
1
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0answers
43 views

Calculating first harmonic of second sound

I can't find some of the values I need for this calculation, which I'm trying to do prior to an experiment around superfluidity. Specifically I am trying to get a rough estimate of the first harmonic ...
1
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0answers
53 views

Capturing superfluid condensation with exact diagonalization

Doing exact diagonalization on bosonic systems is tricky, because the possibility of multiple occupancy means that even the single-site Hilbert space is infinite-dimensional. It's my understanding ...
1
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0answers
29 views

Solution to periodic potential GP equation

Consider the boundary condition $\psi(0)=\psi(2\pi)$ and the Hamiltonian (and corresponding nonlinear Schrödinger equation): $$\left[\left(-i\frac{\partial}{\partial\theta}-\Omega\right)^2+2\pi\gamma|\...
1
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0answers
139 views

What is the equation for the elementary-excitation spectrum of superfluid heluim over whole momentum space?

I have a simple question. What is the equation for the elementary-excitation spectrum of superfluid helium over whole momentum space, not just near the origin (i.e., phonon excitations $\epsilon=cp$) ...
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0answers
213 views

$U(1)$ gauge symmetry in superfluid

The conventional superfluid phase in a Bose-Hubbard ground state has $U(1)$ symmetry. In the presence of spin-orbit coupling (SOC), the superfluid ground state has non-uniform phases. Why do people in ...
0
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0answers
17 views

Diamagnetic current in the BdG superconductor

Recently, I am following the paper arXiv:1610.01803 to study superfluid weight. In this paper the diamagnetic current is given by: $j^D_{\mu}(\vec{q})=\sum_{\vec{k},\sigma}\partial_{\mu}\partial_{\...
0
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1answer
27 views

What happens, if a liquid/gas is kept on constant high pressure in a closed container for a long period?

On applying non-increasing constant pressure, I need to understand the case for liquid and gas. If container is not inescapable: Will the liquid/gas heat up? Will any of their properties change? ...
0
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0answers
14 views

What are the types of waves possible in a superfluid?

What are the major types of waves possible (in principle) in a superfluid? I read about sound waves, temperature waves, sound capillary waves, thin film waves, surface waves, spin waves, shock waves, ...
0
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1answer
49 views

Why we can't write low energy effective field theory for a gapless system?

Assume that we have an Hamiltonian $$H=H_0+H_{int}$$ where $H_0$ has gappless excitations and $H_{int}$ has usual two body interactions. If $H_0$ were gapped I would able to get low energy effective ...
0
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1answer
55 views

Resource request: Superfluid helium

I am wondering if anybody could recommend any good textbooks on the subject. So far, I have discovered (but not yet had a chance to read), a chapter in Landau-Lifshitz fluid mechanics (love Landau-...
0
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0answers
152 views

Superconductivity and superfluidity in bosonic and fermionic condensates

Can bosonic and fermionic condensates explain superfluid and superconducting properties? Are they better than the theory of BCS and Landau? Edited: My question is based in this lecture pesentation ...
0
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2answers
65 views

Quantification of the circulation in superfluids : why does the phase jump by $2 \pi$?

In superfluidity we have the current density that is $j=\frac{h}{m} \vec{\nabla}(\phi)$ Where the wavefunction describing the system is : $\psi(\vec r)=\sqrt{n_s}e^{i \phi(\vec{r})}$ We then ...
0
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1answer
72 views

Can superfluids communicate faster than light?

According to this video: https://www.youtube.com/watch?v=ueVTzEB3tJ8 A superfluid "flows without friction" and "all of the atoms in a superfluid are in the same quantum state." What strikes me as odd ...
0
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0answers
207 views

Do superfluids have zero viscosity?

The Wikipedia definition of a super fluid is: Superfluidity is a state of matter in which the matter behaves like a fluid with zero viscosity As a fluid dynamics guy, I have a hard time imagining ...
0
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1answer
24 views

Why the total nuclear spin is only 0 or 2 for singlet s-wave scatting with $M_F=0$?

when I read the lecture of Feshbach resonance, the lecture on page 15 said that it want to find all s-wave molecules for $M_F=0$. It said when the two atoms are singlet, the total nuclear spin is only ...
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0answers
233 views

Why does not the bare interaction potential appear in the Bogoliubov theory?

They use some effective potential defined by the s-wave scattering length, but not the bare atom-atom interaction $V(r)$. Why? It is standard practice in second quantization to use the bare ...
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0answers
140 views

Specific Heat of Liquid Helium

At the lambda point, the specific heat of Liquid Helium diverges. After searching for a curve, I've found only measured curves. Is there a theoretical curve for this transition?
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0answers
84 views

Superfluids (meaning, properties)

I am curious as to what a superfluid is? I have seen videos that say that they have zero viscosity, and I know that it means that there is no friction between the layers of the fluid. But what is its ...
0
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0answers
70 views

Superfluid across a temperature gradient

As I understand it, superfluids cannot sustain temperature gradients; specifically, if a gradient is introduced somewhere on the boundary of the superfluid, a "second sound" thermal wave propagates ...