Ultracold polar molecules in a 3D optical lattice 颜波 Department of physics, Zhejiang University Hangzhou, China. 2016-6-27

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

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

Create ultracold polar molecules w1 w2 3S 1S 1P Inter-nuclear distance R Energy v = 0, N = 0, J = 0 6000 K

How to create ultracold molecules Mg Li Yb Na Rb K Sr Ca Cs NaK RbCs J. W. Park, et al., PRL. 114, 205302 (2015) T. Takekoshi, et al., PRL 113, 205301 (2014) RbNa M. Y. Guo, et al., PRL. 116, 205303 (2016) P. K. Molony, et al., PRL 113, 255301 (2014)

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)

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)

quantum Zeno effect

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, 080405 (2012)

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

dipole-dipole interactions nature communication 6391, 2014

q=0 term nature communication 6391, 2014

SOC term nature communication 6391, 2014

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

Quantum magnetism with polar molecules and Energy difference between Explain more here. Spin exchange (XY) A. V. Gorshkov, et al, Phys. Rev. A 84, 033619 (2011)

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

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

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

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

Experimental measurement Measure the trap frequency. Measure the trap frequencies of KRb and Rb. B. Neyunhuis, et al., PRL 109, 230403 (2012)

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

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, 230403 (2012)

Anisotropic polarizability Ramsey spectroscopy B. Neyunhuis, et al., PRL 109, 230403 (2012)

Optimizing in a 3D lattice

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

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

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 501 521 (2013)

Oscillations in the contrast T (ms) Contrast Fitting function: Theory prediction: . We measure: . Bo Yan, et al, Nature 501 521 (2013)

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

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

Density dependence Collapse of the data |1,-1> |1,0> Molecule filling in lattice: 8% K. Hazzard, et. al., PRL 113, 195302 (2014)

WAHUHA pulse - Bo Yan, et al, Nature 501 521 (2013)

Suppressing the oscillations Ramsey pulse Spin echo pulse Multi-pulse Bo Yan, et al, Nature 501 521 (2013)

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

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

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

ideal condition No external trap heating higher band J. K. Freericks, et al, PRA 81, 011605 (2010)

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

Load the lattice at a=0 S. Moses, et al., Science, 350, 659 (2015) N_Rb=2.8-5.2e3 atoms S. Moses, et al., Science, 350, 659 (2015)

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, 080403 (2005).

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

Further work: Applying the E field J

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

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

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

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

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

Thanks

Tunneling induced loss

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

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

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

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, 521-525 (2013)

Quantum magnetism with polar molecules A. V. Gorshkov, et al, Phys. Rev. A 84, 033619 (2011)

Geometrical factor

Dipole-dipole interactions PRA 76, 043604 (2007), Nat. Phys. 2, 341 (2006).