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Topic: Superfluid


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In the News (Tue 23 Apr 19)

  
  Properties of Superfluid Helium (He II)
Superfluid or Helium II technology has been developed quite successfully in the past decades in both aerospace and magnet cooling systems.
The two fluid model postulated by Landau and Tisza is the most accepted theory for predicting superfluid behavior.
The two fluid model postulates that the density of liquid helium is composed of the density of the superfluid and that of the normal fluid.
www.yutopian.com /Yuan/HeII.html   (456 words)

  
  Superfluid Summary
Superfluidity was first discovered in 1937 in the helium-4 isotope by the Russian physicist Pyotr Leonidovich Kapitza (Nobel Prize in physics, 1978) and it is considered one of the most remarkable breakthroughs of low-temperature physics.
The phase change to the superfluid state in helium-4 is referred to as the lambda transition, because the shape of the specific heat curve vs. temperature resembles the Greek letter lambda(λ).
Superfluids are also used in high precision devices such as gyroscopes, which allow the measurement of some theoretically predicted gravitational effects, for example see Gravity Probe B article.
www.bookrags.com /Superfluid   (1420 words)

  
 Black Light Power, Inc.
Free electrons are trapped in superfluid helium as autonomous electron bubbles interloped between helium atoms that have been excluded from the space occupied by the bubble.
Superfluid helium is an ideal medium to study individual trapped electrons in much the same way that individual ions may be studied in Penning traps.
Electrons bubbles in superfluid helium reveal that the electron is real before it reaches the detector and that a physical interpretation of the wavefunction is necessary.
www.blacklightpower.com /theory/superfluid.shtml   (345 words)

  
 Two Fluid Model of Superfluid Helium (He II, Superfluidity)
In 1938, Kapitza and independently Allen and Misener reported that there is no measurable resistance to the flow of He II through small capillaries with diameter of the order of 10-4 cm (Kapitza 1938, Allen and Misener 1938).
In addition to superfluidity, some of the remarkable properties of He II include extremely high thermal conductivity, the fountain effect, the mechano-caloric effect and the Rollin Film.
Further, the sum of the normal fluid density and the superfluid density is equal to the bulk fluid density
www.yutopian.com /Yuan/TFM.html   (0 words)

  
 Physics Today February 2001
Superfluid phenomena in liquid helium-4 have fascinated both experimentalists and theoreticians since the discovery of superfluidity in 1938 simultaneously by Peter Kapitsa at the Soviet Academy of Sciences and by Jack Allen and Donald Misener at the Royal Society Laboratories in Cambridge, England.
Initially, it was unclear whether the sharp rotational lines might merely be a consequence of the extremely weak van der Waals interactions of He atoms with molecules, or are somehow related to the superfluidity of the medium.
He on substrates such as graphite, where the superfluid fraction in the layer closest to the substrate is depleted as a result of the relatively strong van der Waals interactions with the substrate.
www.physicstoday.org /pt/vol-54/iss-2/p31.html   (3347 words)

  
 Superfluid helium as a vacuum (June 1998) - Physics World - PhysicsWeb
The physics of the superfluid drop is easy to understand and calculate using the path integral technique introduced by Richard Feynman in 1953.
Feynman explained that the superfluid state is an entangled liquid of these loops, with many loops extending right across the sample (see figure).
The best definition of superfluidity, originally given by Lev Landau in 1941, is precisely what is measured in the Göttingen experiment: the response of the fluid to the motion of an impurity.
www.physicsweb.org /article/world/11/6/3/1   (1147 words)

  
 Physicists Observe Transition of a Gas to a Superfluid for First Time
For the first time, MIT scientists have directly observed the transition of a gas to a superfluid, a form of matter closely related to the superconductors that allow electrical currents to travel without resistance.
When the atoms are cooled down, the appearance of superfluidity is accompanied by a sudden change in the shape of the cloud.
Properties of superfluid ultracold fermions are also being studied by teams at the University of Colorado at Boulder, the University of Innsbruck in Austria, the École Normale Supérieure in Paris, Duke University and Rice University.
www.azom.com /details.asp?newsID=6089   (704 words)

  
 Superfluid helium-4 whistles just the right tune
According to Packard and Hoskinson, the purity of the tone may lead to the development of rotation sensors that are sufficiently sensitive to be used for Earth science, seismology and inertial navigation.
In the case of superfluids, however, a pressure difference across a tiny hole would cause a vibration in the superfluid at a frequency - the Josephson frequency - that increases as the pressure increases.
While working with an array of holes 70 nanometers across, essentially testing the apparatus with helium-4 before using it to conduct a helium-3 experiment, Hoskinson was surprised when he put on earphones and heard the characteristic pennywhistle sound as the pitch dropped with the pressure in the device.
www.eurekalert.org /pub_releases/2005-01/uoc--shw012805.php   (870 words)

  
 New model describes avalanche behavior of superfluid helium
By utilizing ideas developed in disparate fields, from earthquake dynamics to random-field magnets, researchers at the University of Illinois have constructed a model that describes the avalanche-like, phase-slip cascades in the superflow of helium.
Their intent was to amplify the feeble whistling sound of phase-slips associated with superfluid helium passing through a single nano-aperture by collecting the sound produced by all of the apertures acting in concert.
The main components of the researchers' model are nano-apertures possessing different temperature-dependent critical flow velocities (the disorder), and inter-aperture coupling mediated by superflow in the reservoirs (the interactions).
www.chemlin.net /news/2007/apr2007/superfluid-helium.htm   (0 words)

  
 01.27.2005 - Superfluid helium-4 whistles just the right tune
According to Packard and Hoskinson, the purity of the tone may lead to the development of rotation sensors that are sufficiently sensitive to be used for Earth science, seismology and inertial navigation.
In the case of superfluids, however, a pressure difference across a tiny hole would cause a vibration in the superfluid at a frequency - the Josephson frequency - that increases as the pressure increases.
While working with an array of holes 70 nanometers across, essentially testing the apparatus with helium-4 before using it to conduct a helium-3 experiment, Hoskinson was surprised when he put on earphones and heard the characteristic slide whistle sound as the pitch dropped with the pressure in the device.
www.berkeley.edu /news/media/releases/2005/01/27_helium4.shtml   (931 words)

  
 Access Science And Technology - New Matter: Friction Free Hydrogen   (Site not responding. Last check: )
Although a number of this century's outstanding physicists have contributed to the understanding of superfluidity, it remains one of the fascinating phenomena of physics.
The effect is similar to a laser beam, notes Ceperley, in that in both cases -- photons from the laser and helium atoms or hydrogen molecules -- the quantum particles are bosons, particles with integral spin.
It's like rotation to a superfluid." Similarly, as it's possible to establish current in a superconducting circuit that will flow forever, superfluid helium can be made to flow in a loop, a "superflow" that continues as long as superfluid conditions are maintained.
access.ncsa.uiuc.edu /CoverStories/Superfluid/Superfluid.html   (1091 words)

  
 CONDENSED MATTER: METALLIC ANALOG OF SUPERFLUID HELIUM-3
The superfluidity of liquid helium is apparently due to the weakness of the attractive force between two helium atoms and to the small atomic mass, which according to laws of quantum mechanics make the atoms difficult to *localize.
A superfluid is considered to be characterized by a macroscopic quantum-mechanical wave function that locks the superfluid into a *coherent state.
The essential idea is that when superfluid helium is in a rotating container, the mathematics of the system wave function are such that a set of discrete microscopic vortex states are produced by each particular set of boundary conditions, and these microscopic vortex states are experimentally observable [*Note #1].
scienceweek.com /2004/sa041224-1.htm   (2074 words)

  
 MIT physicists shed new light on superfluidity - MIT News Office
The superfluid gas created at MIT can also serve as an easily controlled model system to study properties of neutron stars or the quark-gluon plasma that existed in the early universe.
When the atoms are cooled down, the appearance of superfluidity is accompanied by a sudden change in the shape of the cloud.
Properties of superfluid ultracold fermions are also being studied by teams at the University of Colorado at Boulder, the University of Innsbruck in Austria, the ��cole Normale Sup̩rieure in Paris, Duke University and Rice University.
web.mit.edu /newsoffice/2006/superfluidity.html   (754 words)

  
 ARCADE Superfluid Pumps
But the fraction of the liquid in the superfluid state can only depend on the temperature, which is fixed: as the superfluid moves through the plug, some if it gets converted to normal fluid.
The newly-minted normal fluid is blocked by the plug and must remain in the tube, and so the gradient remains until the flow of liquid into the tube increases the pressure enough to counter the superfluid gradient across the plug.
As before, superfluid helium will flow across the plug from A to B. The extra liquid stuck on side B increases the volume on side B by an amount dV, raising the liquid level and creating a pressure head dP.
arcade.gsfc.nasa.gov /pumps.html   (949 words)

  
 What is a Superfluid?   (Site not responding. Last check: )
The key difference between atom pairing in a superfluid and electron pairing in a superconductor is that the atomic pairing is mediated by quantum spin fluctuations rather than by phonon (vibratory energy) exchange.
A superfluid has zero thermodynamic entropy and infinite thermal conductivity, meaning that no temperature differential can exist between two superfluids or two parts of the same superfluid.
The potential applications of superfluids are not as exciting and wide-ranging as those of superconductors, but dilution refrigerators and spectroscopy are two areas where superfluids have found use.
www.wisegeek.com /what-is-a-superfluid.htm   (499 words)

  
 Superfluid Droplets on a Solid Surface   (Site not responding. Last check: )
Superfluid helium has unusual thermal and mechanical properties[1] and is well known for it ability to spread over surfaces and to flow without dissipation through even microscopic holes.
Despite the superfluidity of the drops, the value of the contact angle which we observed depended critically on the way the drop was prepared.
Superfluid droplets on cesiated substrates have remarkable spreading and flow properties that are not simple consequences of bulk superfluid behavior.
www.physics.uci.edu /~lowtemp/drops/paper.html   (1668 words)

  
 Second superfluid state of matter proposed   (Site not responding. Last check: )
Superfluidity, which is defined as the movement of liquid without friction, was first discovered in 1938.
Zhang argues that this intermediate stage is a new state of matter, one in which the fluid is dominated by a series of clockwise and counterclockwise superfluid eddies that form a relatively stable lattice, analogous to that formed by the atoms in an ionic crystallike salt.
So what he observed was a phase in which sound waves behaved in a manner that differed both from those traveling in an ordinary liquid or in a superfluid.
www.stanford.edu /dept/news/pr/94/940321Arc4370.html   (516 words)

  
 Theory
In this case, the superfluid component will cause the speed of first sound to continually decrease as the temperature is increased from about 1 K, with a discontinuity at the lambda point, as shown in figure 2.
are the densities of the superfluid component and normal component respectively, T is the absolute temperature, S is the entropy of the liquid (contained in the normal component), and C is the heat capacity.
Due to the fact that superfluid liquid helium has zero viscosity, but the normal component has a certain amount of viscosity, we are able to manipulate a situation in order to prevent the normal component from flowing while allowing the superfluid to move about freely.
mxp.physics.umn.edu /s03/Projects/S03He/theory.htm   (2649 words)

  
 Superfluid Helium   (Site not responding. Last check: )
The liquid helium is pumped down to the lamda point transition where it is observed to suddenly become quiescent once the superfluid state is achieved.
The creep effect, or self siphoning, is the consequence of the superfluid property of having zero viscosity.
It is performed by raising a small bucket above the superfluid, as shown in the photo at right, and letting the bucket drip until it is entirely empty.
www.physics.brown.edu /physics/demopages/Demo/thermo/demo/7a7050.htm   (326 words)

  
 EETimes.com - MIT researchers spin superfluid gas   (Site not responding. Last check: )
The team observed fermionic superfluidity in a lithium-6 isotope consisting of three protons, three neutrons and three electrons.
The work is based on the MIT group's earlier creation of Bose-Einstein condensates, a form of matter in which condensed particles act as a big wave.
The superfluid Fermi gas can also serve as an easily controlled model system to study the properties of much denser forms of fermionic matter such as solid superconductors, neutron stars or the quark-gluon plasma that existed at the beginning of the universe.
www.eetimes.com /news/latest/showArticle.jhtml;jsessionid=DBRHIOL3VCACWQSNDBGCKH0CJUMEKJVN?articleID=164901884&printable=true   (489 words)

  
 Slashdot | First Experimental Success of a Superfluid
Superfluid materials are well-known; the first example, the boson [wikipedia.org] helium-4, was discovered in 1937.
The superfluidity of helium-3, a fermion [wikipedia.org], was shown to be a superfluid in the 1970s.
Superfluidity occurs when particles pair up (half spin-up and half spin-down) to produce a material without viscosity, in a manner analogous to that of the electron Cooper pairs [wikipedia.org] of superconductivity.
rss.slashdot.org /Slashdot/slashdotScience?m=517   (2255 words)

  
 MIT physicists create new form of matter - MIT News Office
This gives a rotating superfluid the appearance of Swiss cheese, where the holes are the cores of the mini-tornadoes.
The MIT team was able to view these superfluid vortices at extremely cold temperatures, when the fermionic gas was cooled to about 50 billionths of one kelvin, very close to absolute zero (-273 degrees C or -459 degrees F).
The superfluid Fermi gas created at MIT can also serve as an easily controllable model system to study properties of much denser forms of fermionic matter such as solid superconductors, neutron stars or the quark-gluon plasma that existed in the early universe.
web.mit.edu /newsoffice/2005/matter.html   (960 words)

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