Experimental Study Of Interaction Of ⁶Li And ⁴¹K Atoms And Development Of Techniques Of Optical Lattice

This thesis mainly describes four experimental research work based on ultra-cold 6Li-41K atoms during my Ph.D.At the begi1ning,we introduce the background,of which how the ultra-cold atom system has developed into an ideal platform for study-ing strongly correlated systems from two aspects,which are the ultra-cold atoms near the Feshbach resonance or in an optical lattice.Then,we introduce the properties of Boson and Fermi gas,the expansion dynamics of strongly interacting fermi gas,and the Feshbach resonance in 2nd chapter,respectively.Next,we introduce the basic concepts of both of optical trap and optical lattice,the band structure of optical lattice,the Fermi Hubbard model in 3rd chapter,respectively.From the 4th chapter,we enter the field of the ultra-cold atom experiment.We first briefly introduce our ultra-cold 6Li-41K ex-perimental platform.Based on this platform,we have finished four important research work.In the 1st work,we observe a tunable and broad d-wave shape resonance of 41K boson gas with a triplet structure by performing inelastic loss measurements,and mea-sure molecular binding energies through magnetic field modulation spectroscopy,of which the results agree very well with multichannel quantum defect theory(MQDT).The measured lifetime of atoms near the resonance is found to be much longer than the typical many-body equilibrium time.The measurement and analysis of the breathing mode,which is excited by ramping magnetic cross the resonance,strongly suggests that a low-temperature atom-molecule mixture is produced.In the 2nd work,we observe the expansion dynamics of fermi superfluid in BEC-BCS crossover,which is evaporated by a cigar-shaped optical trap,in a saddle potential.At 0.06(1)TF low temperature,atomic cloud will undergo an anisotropic hydrodynamic expansion over 30 ms,which behaves like an out-of-phase oscillatory expansion in the horizontal plane.By analyzing the expansion dynamics with hydrodynamic equation,we can extract the effective polytropic index ? of the exponential Equation-of-State(EoS)of Fermi superfluid.The extracted y show a non-monotonic behavior in the BEC-BCS crossover,and the values of y in unitarity and BEC side agree well with the results of theoretical calculation.In the 3rd work,we find that there is an inelastic hyperfine-changing collision be-tween 6Li in the lowest Zeeman ground state and 41K in the highest Zeeman ground state,and directly observe the collisional products and measure the spin-changing dy-namics.Based on a two-body collision model,we can obtain the spin-changing rate by simultaneously fitting the experimental results,which agrees well with the result of MQDT.Furthermore,we extract contact parameter of 6Li-41K atoms from the collision dynamics,which is consistent with the calculation of the first order perturbation theory in the weakly-interacting limit.In the last work,we mainly introduce the preparatory work of the optical lattice,which will provide the technical support for the future work,which is the quantum simulation of the phase diagram of the doped Hubbard model and the exploration of the mechanism of high-TC superconductor.The content mainly includes the experimental setup of the 3D optical lattice and ID superlattice,the alignment and the calibration of the optical lattice,and a series of development of the probing techniques of optical lattice.