Experimental Study Of ⁸⁷Rb Ultracold Atoms In Optical Lattice And Quasi–two-dimensional Systems

In the research field of many body physics and many quantum materials,the ultracold gas has become an effective and convenient tool.Because of its large scale,controllable and observable physical properties,ultracold gases are used to study many microscopic worlds that cannot be directly observed.Nowadays,the quantum simulation of hot gas mainly includes the following aspects:spin orbit coupling,quantum phase transition,optical tweezers and atomic array,non-equilibrium state physics,low dimensional quantum gas,etc.This paper firstly introduces the experimental equipment and related technology of producing ⁸⁷Rb BEC.In the experiment,the phase space density and atomic number of the first stage magneto-optical trap are increased by the dark magneto-optical trap.Then,several overlapping coils are used to transport cold atoms to the second ultra-high vacuum glass chamber.Then,after the optical plug magnetic trap evaporation and the crossing optical dipole trap evaporation,⁸⁷Rb BEC is prepared with the number of7 10.In the experiment,the stable magnetic field can provide a guarantee for the Landau-Zener tunneling between atomic energy levels and the experimental data.Eliminating the noise of the digital channel has met the daily requirements,and the accuracy of the magnetic field can reach 0.4m G.High-resolution imaging has long been used in quantum phase transitions,and in recent years,it has played an important role in other research areas.In this paper,the objective parameters and the design of the experimental device are introduced in detail.In the next step,the digital micromirror device(DMD)is used to realize the modulation of the atomic optical potential well,which provides a useful tool for the observation and simulation of quantum many body physics in real space.Raman transition is often used in experiments.In this paper,the theoretical knowledge of Raman transitions is introduced in detail.On this basis,the effect of phase on the intensity of Raman coupling is studied by superposition of two pairs of Raman beams.The phase jitter is eliminated by a clever optical path design,the Raman coupling intensity is modulated by controlling the driving signal of the acousto-optic modulator of one of the laser beam,and the phase of the system could be changed,which directly verifies the theoretical scheme.Vortex is thought to be one of the characteristics of many topological quantum materials,Skyrmions have been deemed to be the future storage devices,because of the low power consumption and extremely small size.In recent years,magnetic Skyrmions has been selected realized in ultracold atoms.In this paper,the experimental scheme of spin-orbit angular momentum coupling is introduced in detail,which will provide a valuable experimental basis for the further study of Skyrmions.There is no complex light path near the secondary glass chamber,so there is enough space to build a three-dimensional optical lattice.Using the Raman transition technique,the quantum properties of Weyl semiconduction can be studied and simulated.It is also possible to build a two-dimensional optical lattice and use Kapitza-Dirac scattering technique to modulate the sub-wavelength phase structure of BEC,which provides a powerful tool for exploring the fine structure of lattice cells and topological defects in matter waves.Atoms in optical lattice potential depth could be ajust by wavelengths,polarizations of optical lattice laser and magnetic field named spin-dependent optical lattice,which can appear two very interesting phenomena,one is magic wavelength(two atomic states of Zeeman levels have same ac Stark shift),the other one is phantom zero wavelength(the ac Stark shift is canceled for one spin state).These two wavelengths is applied widely in optical lattice clocks and material selection.The Gross-Pitaevskii equation(GPE)of low-dimensional BEC is different from the three-dimensional BEC,so it has many special properties and is an important tool for studying non-equilibrium physics,especially for simulating many body localization(MBL).One dimensional system is usually used to study Tonk gas and two-dimensional Bose gas is often used to study Berezinski-Kosterlitz-Thouless(BKT).This paper describes in detail how to use a one-dimensional optical lattice to dynamically modulate the optical lattice period to compress atoms into a two-dimensional regime and obtain a quasi-two-dimensional gas.This work provides a good experimental platform for the future study of low-dimensional gases.