1. Ultracold polar molecules in a 3D optical lattice颜波
Department of physics, Zhejiang University Hangzhou, China.

2. Outline Why polar molecules Polar molecules in a 3D optical lattice
Spin exchange interactions with polar molecules
Increasing the lattice filling

3. Why molecules - Interaction effects
Quantum gas microscope, Greiner group
BEC-BCS crossover
Jin group, JILA
Penning trap of Be ions, Bollinger group
Studying interactions
Long range,
anisotropic,
dipole-dipole
Interactions.
Microscopy of Rydberg excitations, Bloch group
Quantum chaos in Er, Ferlaino group
KRb molecules

4. Create ultracold polar moleculesw1 w2 3S 1S 1P
Inter-nuclear distance R
Energy
v = 0, N = 0, J = 0
6000 K

5. How to create ultracold moleculesMg Li Yb Na Rb K Sr Ca Cs
NaK
RbCs
J. W. Park, et al., PRL. 114, (2015)
T. Takekoshi, et al., PRL 113, (2014)
RbNa
M. Y. Guo, et al., PRL. 116, (2016)
P. K. Molony, et al., PRL 113, (2014)

6. Chemical reaction Ospelkaus et. al., Science 327, 853 (2010)
Get figures from website
Ospelkaus et. al., Science 327, 853 (2010)
Ni et. al, Nature 464, 1324 (2010)

7. quantum chemistry z  E y x Ni, K. K. et al. Nature 464, 1324 (2010)
de Miranda, M. H. G. et al. Nat. Phys. 7, 502(2011)

8. quantum Zeno effect

9. Loading into a 3D lattice
1，KRb is fermion, isolated in lattice. But dipolar interactions are not.
2, measure the lifetime. With or without E field, it is 20s.
Chotia, et al., PRL 108, (2012)

10. Outline Why polar molecules Polar molecules in a 3D optical lattice
Spin exchange interactions with polar molecules
Increasing the lattice filling

11. dipole-dipole interactions
nature communication 6391, 2014

12. q=0 term
nature communication 6391, 2014

13. SOC term
nature communication 6391, 2014

14. Energy level of KRb molecules
Use ground and first excited rotational states
|1,0>
|1,-1>
270 kHz
200 kHz
N = 1
~2.28 GHz ~
N = 0
|0,0>
Electronic, vibrational, rotational ground state

15. Quantum magnetism with polar molecules
and
Energy difference between
Explain more here.
Spin exchange (XY)
A. V. Gorshkov, et al, Phys. Rev. A 84, (2011)

16. E field dependence J Jz
Electric field
V [arb. u.]

17. Probing the interactions
Coherent Ramsey spectroscopy
Initialize
Read-out
hold time T
π/2
π/2
time
50Hz
5kHz

18. The single-particle dephasing
Reduce the differential light shift.
--magic angle
Spin echo
Initialize
spin echo pulse
Read-out
π/2 π
π/2
time

19. Differential light shift
270 kHz
70 kHz
2.23 GHz
Also mention
Achieve a >99% π-pulse fidelity

20. Experimental measurement
Measure the trap frequency.
Measure the trap frequencies of KRb and Rb.
B. Neyunhuis, et al., PRL 109, (2012)

21. Band structure and parametric heating
Optical lattices have band structure.
Parametric heating
0 Erec
20 Erec
60 Erec
Free particle
Flat bands

22. Anisotropic polarizability
Parametric heating in lattice (modulate the laser intensity for 5ms)
|1,-1>
|1,1>
|1,0>
2.2 GHz
|0,0> Rb
B. Neyunhuis, PRL 109, (2012)

23. Anisotropic polarizability
Ramsey spectroscopy
B. Neyunhuis, et al., PRL 109, (2012)

24. Optimizing in a 3D lattice

25. Probing the interactions
Coherent Ramsey spectroscopy
Initialize
spin echo pulse
Read-out
π/2 π
π/2
time
En.n.
En.n. / 8
Dipole-dipole interactions remain

26. Spin echo spectroscopy
Decoherence due to anisotropic
And long range interactions.

27. Density-dependent decoherence
Change molecular density by holding molecules in the lattice for certain time.
Cluster expansion gives
6-10% filling
Bo Yan, et al, Nature (2013)

28. Oscillations in the contrast
T (ms)
Contrast
Fitting function:
Theory prediction:
We measure:
Bo Yan, et al, Nature (2013)

29. |1,0> instead of |1,-1>
B field
B field
|0,0> to |1,0> has higher spin exchange frequency (104Hz).

30. Spin echo for |1,0>
f=107(3)Hz

31. Density dependence Collapse of the data |1,-1> |1,0>
Molecule filling in lattice: 8%
K. Hazzard, et. al., PRL 113, (2014)

32. WAHUHA pulse -
Bo Yan, et al, Nature (2013)

33. Suppressing the oscillations
Ramsey pulse
Spin echo pulse
Multi-pulse
Bo Yan, et al, Nature (2013)

34. Outline Why polar molecules Polar molecules in a 3D optical lattice
spin exchange interactions with polar molecules
Increasing the lattice filling

35. Molecule filling in a 3D optical lattice
Molecule filling effects the dynamics
percolation threshold for infinite 3D system with nearest neighbor interaction ~0.3
5 t
53 t
physics reason for percolation

36. General idea and strategy
One Rb and one K in one lattice site.
Rb multiple occupancy.
K filling is low.
overlap of N=1 regime for both Rb and K
Challenges:
Bosons and fermions require different conditions for N=1 shell.
Entropy is different.
Dual insulators

37. ideal condition No external trap heating higher band
J. K. Freericks, et al, PRA 81, (2010)

38. External trap
S. Moses, et al., (Accepted by Science)

39. Load the lattice at a=0 S. Moses, et al., Science, 350, 659 (2015)
N_Rb= e3 atoms
S. Moses, et al., Science, 350, 659 (2015)

40. Cross the Feshbach resonance
Rb |1,1>+K|9/2,-9/2>
Rb |1,1>+K|9/2,-9/2>
Rb |1,1>+K|9/2,-7/2>
M. Kohl, et al., PRL. 94, (2005).

41. Increasing the filling
Molecule filling in lattice ~ 30%
Old result: 8%
S. Moses, et al., Science, 350, 659 (2015)

42. Further work: Applying the E fieldJ

43. Shift of microwave transition
Energy
Convert this to shift in electric field
E-field
The frequency shifted by about 60 kHz in 1.5 hours
About a 1.5 V/cm shift

44. KRb generation 2 Much better control over the electric field
ITO plates and four rods for flat fields and gradients
Draw my own picture for the selection of pancakes

45. Much better optical access
Glass cell from Precision glassblowing
NA=0.53 microscope objective for imaging along gravity

46. Summary Chemical reactions Ultracold sample Tune aK-Rb
N=1 for Rb and K
Flip K spin
Suppressed by
a 3D lattice
Control all degrees
of freedom
Spin-exchange
interactions
High lattice filling
Many-body physics

47. Acknowledgements KRb Team Jun Ye Deborah Jin Steven Moses Jacob Covey
Matthew Miecnikowski
Zhengkun Fu
Bo Yan
Bryce Gadway
Ana Maria Rey
Murray Holland
John Bohn
Kaden Hazzard
Bihui Zhu
Michael Wall
Johannes Schachenmayer
Goulven Quéméner
Michael Foss-Feig
Mikhail Lukin
Norman Yao
Svetlana Kotochigova
Alexander Petrov

48. Thanks

49. Tunneling induced loss

50. Effective loss rate Strong loss regime: - Multi-band - Single band
B. Zhu et. al, (PRL)

51. Quantum Zeno scaling Tunneling dependence: change x-lattice depth
On site loss dependence:
change y,z-lattice depths

52. Quantum Zeno scaling Tunneling dependence: change x-lattice depth
On site loss dependence:
change y,z-lattice depths

53. Looking at the contrast decay
Scan the phase of the final pulse to obtain a Ramsey fringe 1 1
Spin echo necessary to observe dipolar interactions
Contrast curve decays and oscillates.
B. Yan et al., Nature 501, (2013)

54. Quantum magnetism with polar molecules
A. V. Gorshkov, et al, Phys. Rev. A 84, (2011)

55. Geometrical factor

56. Dipole-dipole interactions
PRA 76, (2007),
Nat. Phys. 2, 341 (2006).