Experimental study of Efimov scenario in ultracold bosonic lithium Lev Khaykovich Physics...
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Transcript of Experimental study of Efimov scenario in ultracold bosonic lithium Lev Khaykovich Physics...
Experimental study of Efimov scenario in ultracold bosonic lithium
Lev Khaykovich
Physics Department, Bar-Ilan University,
52900 Ramat Gan, Israel
FRISNO-11, Aussois, 28/3/2011
Outline
Experimental approach - all optical BEC of lithium Exploring Feshbach resonances on F=1 state. Spontaneous spin purification.
Universal quantum states in three body domain (scattering length a is the largest length scale in the system)
Weakly bound Efimov trimers. Log periodic behavior of three-body recombination. Evidence of spin independent short range 3-body physics.
Mapping between the scattering length and the applied magnetic field – direct association of Feshbach molecules.
Conclusions – is the nonuniversal part of the theory nonuniversal?
Experimental system: bosonic lithium
Compared to other atomic species available for laser cooling, lithium has the smallest range of van der Waals potential:
0
41
26
0 3116
amC
r
Thus it is easier to fulfill the universal physics requirement: |a| >> r0
Why lithium?
Experimental system: bosonic lithium
Bulk metal – light and soft
What’s lithium?
Magneto-optically trapped atoms
All optical BEC: optical dipole trapDirect loading of an optical dipole trap from a MOT
0 order (helping beam)
+1 order (main trap)
main trap
helping beam * The helping beam is effective only when the main beam is attenuated
Ytterbium Fiber LaserP = 100 W
w0 = 31 mU = 2 K
= 19.50
w0 = 40 m
N=2x106
T=300 K
N. Gross and L. Khaykovich, PRA 77, 023604 (2008)
Tuning the s-wave scattering length
0
1BB
aa bg
Feshbach resonance
A weakly bound state is formed for positive a – Feshbach molecule
Feshbach resonances on F=1 state
0.060 0.065 0.070 0.075 0.080 0.085 0.090 0.095 0.100-200
-150
-100
-50
0
50
100
150
200
Sca
tteri
ng
len
gth
[a0]
Magnetic field [T]
black: 11;11red: 10;11green: 10;10yellow: 1-1;10cyan: 1-1;1-1
Theoretical prediction for Feshbach resonances
S. Kokkelmans, unpublished
Search for Feshbach resonances
Positions of Feshbach resonances from atom loss measurements:
Narrow resonance: 845.8(7) G Wide resonance: 894.2(7) G
From the whole zoo of possible resonances only two were detected.
Atoms are optically pumped to F=1 state.
Spontaneous spin purificationSpin selective measurements
to identify where the atoms are. Spin-flip collisions:
|F=1, mF=0>
N. Gross and L. Khaykovich, PRA 77, 023604 (2008)
Feshbach resonances on mF=0 stateTheoretical prediction for Feshbach resonances
This is not the absolute ground state!
Experimental playground
The one but lowest Zeeman stateAbsolute ground state
Three-body universality: Efimov qunatum states
Quantum states near two-body resonance (Efimov scenario)
Universal three-body bound states
weakly bound trimers
even moreweakly bound
trimers
Universal three-body bound states
Position of an Efimov state is nonuniversal. It is defined by a three-body parameter.
Experimental observables – Efimov resonances
Three atoms coupleto an Efimov trimer
One atom and a dimer couple to an Efimov trimer
Experimental observable - enhanced three-body recombination
Three-body recombination
Release of binding energy causes loss which probes 3-body physics.
Manifistation of Efimov resonances
Three atoms coupleto an Efimov trimer
One atom and a dimer couple to an Efimov trimer
Enhanced three-body loss: collisions at much larger distance
Experimental observables – suppressed three-body recombination
There are two paths for the 3- body recombinationtowards deeply
bound state
Suppressed three-body recombination
deeply bound molecule
Two paths interfere destructively a certain scattering lengths – recombination minima.
Three-body recombination theory
NnKN 23 K3 – 3-body loss coefficient [cm6/sec]
Loss rate from a trap:
Dimension analysis: m
aK
4
3
Full treatment: m
aaCK
4
3 3
Effective field theory
42
022 18.16sinhlncos1.67 eaaseaC
2
02 sinhlnsin
2sinh4590
aasaC
0a
0a
Loss into shallow dimer Loss into deeply bound molecules
Efimov resonancesRecombination minima
Braaten & Hammer, Phys. Rep. 428, 259 (2006)
Experimental results
N. Gross, Z. Shotan, S. Kokkelmans and L. Khaykovich, PRL 103, 163202 (2009); PRL 105, 103203 (2010).
a > 0: T= 2 – 3 K
a < 0: T= 1 – 2 K
mf = 1; Feshbach resonance ~740G.
Experimental resultsa > 0: T= 2 – 3 K
a < 0: T= 1 – 2 K
mf = 1; Feshbach resonance ~740G.mf = 0; Feshbach resonance ~895G.
N. Gross, Z. Shotan, S. Kokkelmans and L. Khaykovich, PRL 103, 163202 (2009); PRL 105, 103203 (2010).
Experimentally demonstrated Efimov features
This resonance
This minimum
Experimentally demonstrated Efimov features
Theses two resonancesare related by 22.7
Experimentally demonstrated Efimov features
Theses two resonancesare related by 22
Experimentally demonstrated Efimov features
This resonance
This minimum
This resonance
Summary of the results
The universal factor of 22.7 is confirmed across the region of
Three-body parameter is the same (within the experimental errors) for both nuclear-spin subleves.
a+/|a-| = 0.96(0.3)
Fitting parameters to the universal theory:
a
UT prediction:
N. Gross, Z. Shotan, S. Kokkelmans and L. Khaykovich, PRL 103, 163202 (2009); PRL 105, 103203 (2010).
Mapping between the scattering length And the applied magnetic field
Mapping between the scattering length and the applied magnetic field
0BBEb
2
2
maEb
Bare state (non-universal) dimer:
Feshbach molecule (universal dimer):
Universal two-body bound state
The size of the bound state is that of a
singlet potential: ~1.5 nm
Progressive contamintion by
the atomic continuum
There is only a small fraction of
the wave function in the bound
state. The size of the bound state
increases.
“Quantum halo states”
2
2
maEb
Experimental probe
Deeply bound molecule
Loss mechanism from the trap (release of binding energy):
Mapping between the scattering length and the applied magnetic fieldPrecise characterization of Feshbach resonances by rf-spectroscopy of universal dimers.
A typical RF spectrum
N. Gross, Z. Shotan, O. Machtey, S. Kokkelmans and L. Khaykovich, C.R. Physique 12, 4 (2011) ; arXiv:1009.0926
Mapping between the scattering length and the applied magnetic fieldPrecise characterization of Feshbach resonances by rf-spectroscopy of universal dimers.
Solid (dashed) line – local (global) analysis
N. Gross, Z. Shotan, O. Machtey, S. Kokkelmans and L. Khaykovich, C.R. Physique 12, 4 (2011) ; arXiv:1009.0926
Mapping between the scattering length and the applied magnetic field
0)2(33.34 aaS
0)8(87.26 aaT
Improved characterization of Li inter-atomic potentials.
Precise characterization of Feshbach resonances by rf-spectroscopy of universal dimers.
N. Gross, Z. Shotan, O. Machtey, S. Kokkelmans and L. Khaykovich, C.R. Physique 12, 4 (2011) ; arXiv:1009.0926
Conclusions For two different Fesbach resonances on two different
nuclear-spin sublevles of the same atomic system we demonstrate: Universal scaling factor of 22.7 across the region of
. Same positions of the Efimov features (within the
experimental errors). First experimental indication that the nonuniversal part
of the universal theory – the three-body parameter – might have some “universal” properties. New insight from Innsbruck group – for three different Feshbach
resonances the Efimov features are the same!
a
People
Eindhoven University ofTechnology, The Netherlands
Servaas Kokkelmans
Bar-Ilan University, Israel