Bose-Einstein Condensation (a tutorial) Melinda Kellogg Wyatt Technology Corporation Santa Barbara, CA June 8, 2010
Satyendra Bose (1894 – 1974)
FermionsBosons
Spin
Elementary particles also spin… electron: spin ½ proton/neutron: spin ½ quark: spin ½ photon: spin 1 graviton: spin 2 Higgs boson: spin 0
half-integral spin: electrons, protons, neutrons… zero or integral spin: Higgs bosons, photons, helium-4 atoms, sodium-23, rubidium-87 atoms… FermionsBosons obey Pauli exclusion principle don’t obey Pauli exclusion principle
Albert Einstein (1879 – 1955)
e - e - e - e - e - e - e - e - Bose-Einstein Condensate
where: Critical Temperature
First Bose-Einstein Condensate (BEC): Superfluid He-4
a better BEC requires weaker interatomic interactions… a diffuse gas
Laser Cooling
stationary atom absorbs green photon
and shortly thereafter re-emits it
slightly detune laser towards the red…
photon passes through, unless…
photon is Doppler shifted appears green to atom atom is moving toward light source,
laser
Laser (Doppler) Cooling cools to ~ 150 μK
Evaporative Cooling
Magnetic Trap
low field seeking high field seeking Magnetic Potential Energy S N
Magnetic Trap
Evaporative Cooling magnetic field strength position
Evaporative Cooling potential energy position
Evaporative Cooling position E magnetic field strength
Evaporative Cooling position E magnetic field strength
Evaporative Cooling position E magnetic field strength
Evaporative Cooling position magnetic field strength
Evaporative Cooling position B ~ 30 MHz magnetic field strength
Evaporative Cooling position magnetic field strength
Evaporative Cooling position E magnetic field strength
Evaporative Cooling cools to < 1 μK
BEC of Sodium Atoms Durfee & Ketterle, Optics Express 2, 299 (1998)
Thank you! (mainly of excitons)