Interference of Two Molecular Bose-Einstein Condensates

Christoph Kohstall

Innsbruck

FerMix, June 2009

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Christ

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Kohst

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Sánch

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Leon

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vFer(Mix)-Team

Interference of atomic Bose condensates

A powerful tool to study Bose gases

Interference meets Fermi gases

Interesting challenges

Fermions form bosonic pairs

strong interaction

Interference of two independent BECs

Andrews et al., Science 275, 637 (1997)

Interference of atomic Bose condensates…

a powerful tool to study Bose gases

Now interference meets Fermi gases

highlights and

interesting challenges

Interference of atom lasers

coherence length

Bloch et al., Nature 403, 166 (2000)

Vortex in BEC

phase jump

Inouye et al., Phys. Rev. Lett. 87, 080402 (2001)

2D

BKT transition

P. Krüger et al., Phys. Rev. Lett. 99, 040402 (2007)

1D

Luttinger liquid

Hofferberth et al., Nature Physics 4,489 (2008)

bosonic pairsof fermions

strong interaction

from atoms to molecules

Fermionic lithium – our workhorse

BEC BCS

molecules many-body pairs

Let‘s open the door!

TOF-Images

TOF=0.4 ms

4 ms

8 ms

12 ms

14 ms

B = 700 G

visibility ~25%

zx

0

80 pixel

250 µm

visibility fringe spacingphase

z

Procedure

AOM CCD

lens

trappingbeam

coils for mag. Feshbach field

Li

beam waist 54 µmωy 2π*20Hzωx , ωz 2π*150Hzmag. field 700 GN↑,↓ 200 0001/kFa 3

separation 64 µm

AOM CCD

lens

trappingbeam

coils for mag. Feshbach field

Li

beam waist 54 µmωy 2π*20Hzωx , ωz 2π*150Hzmag. field 700 GN↑,↓ 200 0001/kFa 3

separation 64 µm

in situ

TOF=0 ms

in expansion

TOF = 14 ms

Expansion

clouds clouds

no slicing necessary

mag

nify

ing

glas

strap

posi

tion

trap

position

trap

posi

tion

trap

position

Relative phase

phase

potential clouds

Same result for independent BECs

TC

Temperature dependence

bars are rms

Interaction strength

Interaction strength

Interaction strength

1/kFa (in situ) 4 1 0

detection efficiency

depletion of BEC

# of collisions

mean field potential

pair breaking

many-body pairs

detection

7% 17% 34% not valid

Ekin<Emfpartial reflection

Ekin>Epairing

no survival

0.1 1 30

pote

ntia

lDepleted part has no common phase

1/kFa (in situ) 4 1 0

detection efficiency

depletion of BEC

# of collisions

mean field potential

pair breaking

many-body pairs

detection

7% 17% 34% not valid

Ekin<Emfpartial reflection

Ekin>Epairing

no survival

pote

ntia

l 0.1 1 30

Interference of molecular BECs

The challenge of strong interaction

Tool for new physics