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Questions tagged [superfluidity]

A flow with no viscosity

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272 views

Landau critical velocity and sound velocity

The definition of Landau critical velocity is $v_L=\min_{q}\{\frac{\omega(q)}{q}\}$, where $\omega(q)$ is the spectrum of excitations. The viscosity vanishes when the object is moving through the ...
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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 ...
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Energy of the excitation in the superfluid

According to the chapter 1.3: Superfluidity, from the book "Methods of Quantum Field Theory In Statistical Physics by A.A Abrikosov, it is written that Consider a Bose liquid at absolute zero, ...
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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 ...
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255 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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Is density fluctuation gapless in superfluid?

Deep in the superfluid phase, the superfluid order parameter $\phi$ can be decomposed into the amplitude (density) mode $\rho$ and the phase mode $\theta$ as $$\phi=\sqrt{\rho} e^{\mathrm{i}\theta}.$$ ...
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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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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 ...
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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 ...
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66 views

Is there a phase coexistence line below the critical temperature $T_c$ in normal to superfluid transition?

In the case of water, there is a phase coexistence line (called the liquid-gas coexistence curve) which ends in a critical point. And this line separates the gas phase from the liquid phase in the P-T ...
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Why do pairing and condensation occur simultaneously in superconductors?

Bose condensation in the weak-coupling limit (such as BCS superconductors) and the strong-coupling limit (like BECs of atoms) can be unified into a single framework by the BEC-BCS crossover. One key ...
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220 views

How does the macroscopic wavefunction build up from a zero value to nonzero value?

I can understand how does spontaneous magnetization (the order parameter in paramagnetic to ferromagnetic transition) gradually build up as the temperature is lowered below the critical temperature. ...
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983 views

What causes liquid helium to climb walls?

It is a phenomenon which can be observed if your search on the web. Apparently liquid Helium can crawl up through walls. Does every superfluid do this crawling action or is it just special for liquid ...
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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 ...
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1answer
912 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 ...
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199 views

Why superfluid is described by interacting with goldstone boson?

I've read chapter about superfluids of Anthony Zee's QFT in nutshell and it is still not clear, why the energy spectrum of massless field only is taken into account to describe superfluid? In that ...
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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 ...
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The two-current model of superconductivity

Standard text books (Landau and Lifshitz etc) explain that the correct macroscopic theory of a superfluid is two-fluid hydrodynamics. A superfluid is made of two components, a viscous normal fluid and ...
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How superfluidity can arise at extremely high temperatures

I'm a mathematicians and I don't have a big knowledge of physics. I've heard that superfluidity can arise inside a neutron star and I've given to understand that this has to do with a hugh density ...
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93 views

Why do superfluid vortices form a lattice?

I often hear that in a superfluid, vortices get arranged in a lattice but I don't understand why and I've been hard pressed to find a discussion of it online. I'm aware that vortices should repel ...
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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?
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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 ...
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1answer
290 views

Symmetry breaking and Superfluid - Mott Insulator transition

I know my question is similar to what mentioned in this post: Symmetry breaking in Bose-Hubbard model. Yet, I don't find it clear. I've in mind a 1D Bose-Hubbard Hamiltonian. Moving from the Mott ...
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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 ...
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What causes Superfluidity?

Superfluidity is the frictionless flow and other exotic behavior observed in liquid helium at temperatures near absolute zero. The unusual behavior arises from quantum mechanical effects. What are ...
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Will a propeller work in a superfluid?

Will a propeller work in a superfluid? Opinions differ.
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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 $\lambda$ ...
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Do superfluids lack inertia and/or don't exist with a finite speed of sound?

I've been reading a few things on other sources about superfluids and what kind of propulsion would work in them. Supposedly a propeller won't work in a superfluid, but I'm having a hard time ...
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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 ...
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225 views

Why are superfluids thermodynamically possible?

I was reading about superfluids and how they can flow without loss of any kinetic energy over time, specifically they can form vortices that rotate indefinitely. However I do not understand why this ...
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115 views

What are the limitations of Gross-Pitaevskij equation?

I'm a mathematician and I'm studying as an aside something about superfluids. If I understood correctly in some kind of superfluids as Bose-Einstein Condensate a wave in the fluid must satisfy the ...
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126 views

How is angular momentum stored in the superfluid component of pulsars?

I am trying to understand current theories about why pulsars glitch. I have come across two explanations that I'm assuming are complementary, but which I am having trouble reconciling. The inner ...
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693 views

What does the term liquid mean in condensed matter physics?

In condensed matter physics, people always say quantum liquid or spin liquid. What does liquid mean?
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Univerality Class and Momentum Space Topology

I'm very interested in learning about Superfluid Vacuum Theory, and one thing I have come across is the statement that the universality classes are protected by momentum space topology. So I was ...
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1answer
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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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Superfluid $\Leftrightarrow$ Bose-Einstein condensate?

On the Wikipedia page on superfluidity one can find the sentence not all Bose-Einstein condensates can be regarded as superfluids, and not all superfluids are Bose–Einstein condensates. So I was ...
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How can helium be liquid at absolute zero, given the Third Law of Thermodynamics? [duplicate]

I learned recently that Helium is a liquid even at 0K. Doesn't that mean that it still have some entropy? If so, does it not violate the postulate of thermodynamics that states that entropy must go to ...
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147 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 ...
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276 views

How to calculate fluid(oil / hydrocarbon) loss under pressure

I'm trying to calculate the amount of fluid that would flow through an area dependant on the amount of pressure that there is. I'd also like to know the rate at which it would flow. Essentially I ...
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231 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 ...
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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|\...
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788 views

Can superfluids pass through ordinary baryonic matter?

Since superfluids consists of integer spin bosons or effective bosonic Cooper-paired fermions, Pauli Exclusion Principle does not apply to them. They can thus occupy the same quantum state as any ...
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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 ...
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283 views

Rotation of superfluid

I have two questions related to rotation of superfluids. Firstly, what is the main reason that superfluid cannot rotate as a whole object ? (I found that it is true in Landau's Statistical Physics but ...
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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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627 views

What is the Single Mode Approximation?

When Girvin and co-workers solved the excited collective modes called magneto-rotons in Fractional Quantum Hall liquids, they used something called the Single Mode Approximation (SMA). My question is: ...
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2answers
285 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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Where should I start learning Landau's theory of superfluidity?

Where should I start learning Landau's theory of superfluidity? For a second year undergraduate.
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Bulk modulus of supercrtical air

For gaseous state air has bulk modulus of ~pressure, but what about bulk modulus values about the supercritical pressure treshold, are these still pretty much same as the pressure or does this ...
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Why is the symmetric phase in a Bose gas not superfluid?

In the theory of superfluidity in weakly interacting Bose gases, one finds that in the symmetric phase the exctitations have the dispersion relation $\omega = \frac{k^2}{2m}-\mu$ with gap $\Delta=-\...