Bose-Einstein Condensation (a tutorial) Melinda Kellogg Wyatt Technology Corporation Santa Barbara,...

Bose-Einstein Bose-Einstein CondensationCondensation

Melinda KelloggWyatt Technology Corporation

Santa Barbara, CAJune 8, 2010

Satyendra Bose(1894 – 1974)

Fermions Bosons

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…

Fermions Bosons

obey Pauli exclusion principledon’t obey

Pauli exclusion principle

Albert Einstein(1879 – 1955)

e-

e-

e-

e-

e-

e-

e-

e-

Bose-Einstein Condensate

where:

m

n

km

nT

Bc

3223

2

23

2

)(

Critical Temperature

First Bose-Einstein Condensate (BEC):

Superfluid He-4KTc 17.2

a better BEC requires weaker interatomic interactions…

a diffuse gas

m

nTc

32

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 fieldseeking

high fieldseeking

Magnetic Potential Energy

BU S

N

BU

BU 0U

Magnetic Trap

Evaporative Coolingm

ag

neti

c fi

eld

str

en

gth

position

Evaporative Coolingp

ote

nti

al en

erg

y

position

Evaporative Cooling

position

E

mag

neti

c fi

eld

str

en

gth

Evaporative Cooling

position

E

mag

neti

c fi

eld

str

en

gth

Evaporative Cooling

position

E

mag

neti

c fi

eld

str

en

gth

Evaporative Cooling

position

mag

neti

c fi

eld

str

en

gth

Evaporative Cooling

position

B ~ 30 MHz

mag

neti

c fi

eld

str

en

gth

Evaporative Cooling

position

mag

neti

c fi

eld

str

en

gth

Evaporative Cooling

position

E

mag

neti

c fi

eld

str

en

gth

Evaporative Cooling

cools to < 1 μK

BEC of Sodium Atoms

Durfee & Ketterle, Optics Express 2, 299 (1998)

Thank you!Thank you!