Superfluidity

superfluidsuperfluidsHigh-temperature superfluidityquantum liquidquantum liquidsSUPERFLOW
Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without loss of kinetic energy.wikipedia
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Viscosity

viscouskinematic viscositydynamic viscosity
Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without loss of kinetic energy.
Zero viscosity is observed only at very low temperatures in superfluids.

Helium

Hehelium IIsuperfluid helium
Superfluidity occurs in two isotopes of helium (helium-3 and helium-4) when they are liquefied by cooling to cryogenic temperatures.
In scientific research, the behavior of the two fluid phases of helium-4 (helium I and helium II) is important to researchers studying quantum mechanics (in particular the property of superfluidity) and to those looking at the phenomena, such as superconductivity, produced in matter near absolute zero.

Lev Landau

LandauLev Davidovich LandauL. D. Landau
The semiphenomenological theory of superfluidity was developed by Lev Landau.
His accomplishments include the independent co-discovery of the density matrix method in quantum mechanics (alongside John von Neumann), the quantum mechanical theory of diamagnetism, the theory of superfluidity, the theory of second-order phase transitions, the Ginzburg–Landau theory of superconductivity, the theory of Fermi liquid, the explanation of Landau damping in plasma physics, the Landau pole in quantum electrodynamics, the two-component theory of neutrinos, and Landau's equations for S matrix singularities.

Bose–Einstein condensate

Bose–Einstein condensationBose-Einstein condensateBose-Einstein condensation
Superfluidity is often coincidental with Bose–Einstein condensation, but neither phenomenon is directly related to the other; not all Bose-Einstein condensates can be regarded as superfluids, and not all superfluids are Bose–Einstein condensates.
In 1938, Fritz London proposed BEC as a mechanism for superfluidity in and superconductivity.

Helium-4

4 HeHe-4 4 He Nuclei
Superfluidity occurs in two isotopes of helium (helium-3 and helium-4) when they are liquefied by cooling to cryogenic temperatures.
When liquid helium-4 is cooled to below 2.17 kelvins (−271.17 °C), it becomes a superfluid, with properties that are very unlike those of an ordinary liquid.

Helium-3

3 HeHelium 3 3 He ("helium 3")
Superfluidity occurs in two isotopes of helium (helium-3 and helium-4) when they are liquefied by cooling to cryogenic temperatures.
At low temperatures (about 2.17 K), helium-4 undergoes a phase transition: A fraction of it enters a superfluid phase that can be roughly understood as a type of Bose–Einstein condensate.

Quantum gravity

quantum theory of gravityquantum theories of gravityQuantization of gravity
It is also a property of various other exotic states of matter theorized to exist in astrophysics, high-energy physics, and theories of quantum gravity.
However, a recent derivation in 3+1 dimensions under the right coordinate conditions yields a formulation similar to the earlier 1+1, a dilaton field governed by the logarithmic Schrödinger equation that is seen in condensed matter physics and superfluids.

John F. Allen

John Frank AllenJack AllenJohn Allen
Superfluidity was originally discovered in liquid helium, by Pyotr Kapitsa and John F. Allen.
At the same time as Pyotr Leonidovich Kapitsa in Moscow, Don Misener and Allen independently discovered the superfluid phase of matter in 1937 using liquid helium in the Royal Society Mond Laboratory in Cambridge, England.

Quantum vortex

quantized vorticesvorticesquantum vortices
Superfluidity in an ultracold fermionic gas was experimentally proven by Wolfgang Ketterle and his team who observed quantum vortices in 6 Li at a temperature of 50 nK at MIT in April 2005.
In most cases quantum vortices are a type of topological defect exhibited in superfluids and superconductors.

Pyotr Kapitsa

Peter KapitzaPyotr Leonidovich KapitsaPiotr Leonidovich Kapitza
Superfluidity was originally discovered in liquid helium, by Pyotr Kapitsa and John F. Allen.
In Russia, Kapitsa began a series of experiments to study liquid helium, leading to the discovery in 1937 of its superfluidity (not to be confused with superconductivity).

Boson

bosonsBosonicinteger spin
Each atom of helium-4 is a boson particle, by virtue of its integer spin.
This property is exemplified by helium-4 when it is cooled to become a superfluid.

Fermion

fermionsFermionichalf-integer spin
A helium-3 atom is a fermion particle; it can form bosons only by pairing with itself at much lower temperatures.
At low temperature fermions show superfluidity for uncharged particles and superconductivity for charged particles.

Liquid helium

heliumliquidliquified helium
Superfluidity was originally discovered in liquid helium, by Pyotr Kapitsa and John F. Allen.
At temperatures below their liquefaction points, both helium-4 and helium-3 undergo transitions to superfluids.

Superfluid vacuum theory

superfluid vacuumBEC vacuumother features
Superfluid vacuum theory (SVT) is an approach in theoretical physics and quantum mechanics where the physical vacuum is viewed as superfluid.
Superfluid vacuum theory (SVT), sometimes known as the BEC vacuum theory, is an approach in theoretical physics and quantum mechanics where the fundamental physical vacuum (non-removable background) is viewed as superfluid or as a Bose–Einstein condensate (BEC).

Neutron star

neutron starsStellar spin-downdying star
The idea that superfluidity exists inside neutron stars was first proposed by Arkady Migdal.
The equation of state of matter at such high densities is not precisely known because of the theoretical difficulties associated with extrapolating the likely behavior of quantum chromodynamics, superconductivity, and superfluidity of matter in such states.

Superconductivity

superconductingsuperconductorsuperconductors
This process is similar to the electron pairing in superconductivity. By analogy with electrons inside superconductors forming Cooper pairs because of electron-lattice interaction, it is expected that nucleons in a neutron star at sufficiently high density and low temperature can also form Cooper pairs because of the long-range attractive nuclear force and lead to superfluidity and superconductivity.
The Cooper pair fluid is thus a superfluid, meaning it can flow without energy dissipation.

Quantum mechanics

quantum physicsquantum mechanicalquantum theory
Superfluid vacuum theory (SVT) is an approach in theoretical physics and quantum mechanics where the physical vacuum is viewed as superfluid.
While quantum mechanics was constructed to describe the world of the very small, it is also needed to explain some macroscopic phenomena such as superconductors, and superfluids.

Wolfgang Ketterle

Superfluidity in an ultracold fermionic gas was experimentally proven by Wolfgang Ketterle and his team who observed quantum vortices in 6 Li at a temperature of 50 nK at MIT in April 2005.
In addition to ongoing investigations of Bose–Einstein condensates in ultracold atoms, his more recent achievements have included the creation of a molecular Bose condensate in 2003, as well as a 2005 experiment providing evidence for "high-temperature" superfluidity in a fermionic condensate.

Macroscopic quantum phenomena

macroscopic quantum phenomenonmacroscopicallyquantum phenomena in macroscopic objects
The best-known examples of macroscopic quantum phenomena are superfluidity and superconductivity; other examples include the quantum Hall effect.

Boojum (superfluidity)

boojumphenomenon in superfluidity
In the physics of superfluidity, a boojum is a geometric pattern on the surface of one of the phases of superfluid helium-3, whose motion can result in the decay of a supercurrent.

Supersolid

super solidsupersolid phase of mattersupersolids
A supersolid is a spatially ordered material with superfluid properties.

Cooper pair

Cooper pairsCooper pairingCooper electron pair
By analogy with electrons inside superconductors forming Cooper pairs because of electron-lattice interaction, it is expected that nucleons in a neutron star at sufficiently high density and low temperature can also form Cooper pairs because of the long-range attractive nuclear force and lead to superfluidity and superconductivity.
Indeed, Cooper pairing is responsible for the superfluidity of helium-3 at low temperatures.

Quantum hydrodynamics

hydrodynamicsquantum liquid
An important system of study in quantum hydrodynamics is that of superfluidity.

Egor Babaev

Babaev E. S.
He coauthored the textbook on modern theory of superfluidity with Boris Svistunov and Nikolay Prokof'ev.

Gravity

gravitationgravitationalgravitational force
The ultimate goal of the approach is to develop scientific models that unify quantum mechanics (describing three of the four known fundamental interactions) with gravity.