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Questions tagged [superfluidity]

A flow with no viscosity

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1answer
779 views

Do we have magnetic monopole? Is charge, according to yesterdays paper on Nature by Ray-Roukokoski-Kandel-Möttönen-Hall (30.01.14) quantized?

As everybody here knows, Maxwell's equation would look more beautiful if a magnetig charge were present. Beyond the aesthetics question, if a single magnetic Dirac monopole would be found, the ...
7
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1answer
1k views

What is the difference between superfluidity and Bose condensation?

My question is about zero-temperature ground state of a Bose system. Suppose that the system stabilizes a BEC order parameter, say $\langle b^+ \rangle$, and fixes its phase. Is this a superfluid? And ...
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2answers
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How to understand the emergent special relativity in the superfluid?

The superfluid vacuum theory was proposed to understand some features of the vacuum (aether) from the emergence point of view. Although made up of non-relativistic atoms, the low-energy excitations of ...
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4k views

Will a propeller work in a superfluid?

Will a propeller work in a superfluid? Opinions differ.
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1answer
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What is off-diagonal long range order in superfluid?

From Wikipedia: [...]Off-diagonal long-range order (ODLRO) [...] exists whenever there is a macroscopically large factored component (eigenvalue) in a reduced density matrix of any order. How to ...
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1answer
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The bizarre behaviour of superfluids! Climbing up walls and geting out of glass beakers

SUPERFLUIDITY: Superfluidity is one of the most amazing quantum phenomena, which we can sit and watch them happening before our eyes! Watch this video, it is only a couple of minutes long, which ...
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2answers
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Superfluidity and superconductivity?

Superfluidity and superconductivity? Is there any relation between the two aside from the fact that they are somewhat analogies , I see a lot of people on the internet who claim the helium (in it's ...
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2answers
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Are all bose-einstein condensates superfluid?

I feel like the answer should be "no" since all superfluids are not strictly BEC since they can undergo a Kosterlitz–Thouless transition in 2D, for example. I believe the ideal gas isn't superfluid, ...
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2answers
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vortex anti-vortex configuration to ground state [closed]

i'm studying kosterlitz transition. I'm reading this: https://assets.nobelprize.org/uploads/2018/06/advanced-physicsprize2016-1.pdf?_ga=2.51324009.1302372948.1538119052-1605759177.1538119052 Now ...
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1answer
241 views

Is dark matter a superfluid?

The fact that the dark matter halos surrounding colliding galactic clusters simply pass through each other without interacting has a simple explanation. If they are superfluid bodies, wouldn't be ...
9
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1answer
2k views

BCS-BEC crossover

It would be really helpful if somebody could describe what does one mean by a BEC-BCS Crossover. I was going through articles available on the topic, but I was unable to grasp the gist of the topic.
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2answers
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Why is chemical potential, μ=0 when calculating critical temperature of BECs?

How do we justify taking the chemical potential, $\mu$ as $0$ when calculating the critical temperature of Bose-Einstein Condensates (BECs)? I apologise as I do not how to use LaTeX, for if I did the ...
6
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1answer
302 views

Does every superfluid have a normal and a superfluid component?

After seeing the question Will a propeller work in a superfluid?, I remembered an old video by Alfred Leitner (1'50'' and 3'00'')where he experimentally shows that liquid Helium below the $\lambda$ ...
2
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1answer
878 views

Intuitive explanation for superfluidity?

I know that superfluidity is caused by the fluid having zero viscosity. This only happens at very low temperature, so the fluid (e.g. Helium-4) is a Bose-Einstein condensate. I also know that in a ...
2
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2answers
278 views

Nomenclature clarification concerning solitons

My experience with solitons is restricted to the classical setting, namely solutions to the quartic interaction $\phi^4$, the Sine-Gordon equation, and Korteweg–de Vries equations. I was explicit to ...
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1answer
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Simple & intuitive explanation of superfluidity?

I know that superfluidity is caused by the fluid having zero viscosity. This only happens at very low temperature, so the fluid (e.g. Helium-4) is a Bose-Einstein condensate. I also know that in a ...
3
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1answer
726 views

Symmetry breaking in Bose-Hubbard model

According to Landau's symmetry breaking theory, there is a symmetry breaking when phase transition occurs. What is the symmetry breaking of superfluid-Mott insulator transition in Bose-Hubbard model?...
2
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1answer
144 views

Rigidity and superflow

In the book "Introduction to Many-Body Physics" by Piers Coleman, it is argued (page 406) that a momentum supercurrent (superflow) corresponds to sheer stress in a crystal. What would be a simple ...
2
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1answer
78 views

Time of flight images of Bose-Hubbard model

on the website of Immanuel Bloch, you can find time of flight images of bosonic particles inside an optical lattice for different values of the depth of the lattice. (http://www.quantum.physik.uni-...
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3answers
220 views

A Strange Plastic (as opposed to Elastic) Balloon?

Today, while contemplating on the absurdity of life (or, in other words, procrastinating as usual), I stumbled across a strange inflated balloon, the first of its kind that I have ever seen as per my ...
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1answer
237 views

Partition function of weakly interacting Bose gas

In the Bogoliuobov theory of superfluidity, the hamiltonian of a system of weakly interacting bosons in second quantized notation is diagonalized with the following result: $$\hat H = H_0 \hat1 + \...
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1answer
116 views

Vortex in superfluid?

I'm studying superfluid helium 4. I have studied that the superfluid has a velocity : $ \vec{v}_s = \frac{\hbar}{m} \vec{\nabla} \varphi(\vec{r}) $ $\rightarrow$ $ \nabla \times \vec{v}_s = 0 $. (...
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2answers
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Can anyone explain what a superleak is?

In the context of Helium can anyone explain what a superleak is and why it could be useful?