B.E.C.(Bose-Einstein Condensation)

발표자 : 이수룡 (98)

Physics

Quantum Physics

Quantum Statistics

Predicted 1924……Created 1995

The Nobel Prize in Physics 2001

USA(Eric A.Cornell,1961)

Germany(Wolfgang Kettlerle,1957)

USA(Carl E.Wieman,1951)

Spin Classification

Fermions : odd half integer spinBosons : integer spinIt determines the nature of the energy distribution in a collection of the particles.

Fermions

Enrico Fermi, Paul A.M. Dirac described the special properties of this type of particles.Fermi-Dirac statistics, Pauli exclusion principleno two identical fermions can be in exactly the same quantum state electrons, protons, neutrons, muons, quarks, ....

Bosons

In 1924 Bose made an important theory regarding light particles. Einstein extended it. Bose-Einstein statisticsan unlimited number of identical bosons in exactly the same state photons, 4He atoms, pions, ....

Bose-Einstein Condensation

From Bose-Einstein CondensationA phase transition at low enough temperaturesBose did not find it.

Laser cooling and trapping

Laser beams slow down atoms by the Doppler shift.Then trappingThis is called “optical molasses”.To 10^-4 K

Evaporative cooling

Magnetic trappingTo 10^-6 KThe particle having the high energy escapes from the magnetic trap.The total temperature is decreased.

Look like?

References

Physics 2000Hyperphysics by Georgia State UniversityThe Nobel Prize in Physics 2001http://press.web.cern.ch/pdg/particleadventure/frameless/fermibos.htmlhttp://musr.physics.ubc.ca/~jess/p200/spin/node8.htmlhttp://musr.physics.ubc.ca/~jess/p200/spin/node7.html