The Magnetically Tuned Feshbach Resonance Of High Partial Wave In The Ultracold Atoms And Its Modulation By Electric Field

Due to the strong quantum controllability,ultracold atomic gas is an ideal system for investigating quantum effects.In ultracold diatomic scattering,the magnetic field can be used to adjust the energy difference between different scattering channels.The magnetically tuned Feshbach resonance occurs when the bound-state energy of the closed channel approaches the threshold of the incident channel,and the atomic interaction changes in the vicinity of the resonance.The centrifugal barrier suppresses the high partial-wave scattering,and high partial-wave Feshbach resonances are narrow.In this paper,we investigate theoretically the high partial-wave Feshbach resonance at different collision energies and its modulating action by external electric field.The modulating action of an external electric field on the magnetically tuned Feshbach resonance in ultracold heteronuclear atomic collision is investigated by using the multichannel quantum-defect theory(MQDT).By taking the 6Li-40K collision system as an example,we colstruct singlet and triplet quantum defect matrices y(0)and y(1)which include the coupling between different partial waves induced by electric field.By taking the truncated-C6/R6C8/R8-C10/R10 potential as the reference potential,quantum-defect parameters for s-,pand d-wave scattering are calculated to investigate the modulating action of the electric field on the resonance position and width.The interaction of the electric field with the dipole moment of the collision complex shifts the resonance position and changes the resonance width.The stronger the electric field,the greater the effect.In addition,the electric field may induce a new resonance feature,referred to as electric-field-induced Feshbach resonance.Resonance splitting appears when the electric field is not parallel to the magnetic field.The results calculated by using the MQDT agree with the ones by the close-coupling(CC)method,while computational cost decreases greatly.We present animated contour plots of elastic and inelastic cross sections as functions of magnetic field B and collision energy Ecol for the ultracold 85Rb-87Rb collision system by using the CC method,which aids in the investigation of magnetically tuned Feshbach resonance behaviour above the threshold.Resonance peaks decay with the increase of the collision energy.It is found that the "resonance tail" appears at the given magnetic field when the cross section decreases from the maximal value of the resonance peak to the minimum value.The self-energy at the threshold,which represents the coupling strength between open and closed channels,is considered as a critical parameter to quantitatively describe properties of Feshbach resonances.For a small absolute value of the self-energy at the threshold,the resonance tail is long.A long resonance tail indicates an appreciable resonance in a relatively large region of collision energy.This relationship between the self-energy and properties of Feshbach resonances still exists in the thermally averaged inelastic rate coefficient.The bound-state energies for high partial waves split owing to the spin-spin interaction,which results in multiple nearly overlapping resonances.However,multiple nearly overlapping resonances for high partial waves are difficult to resolve in thermally averaged rate coefficients.The above findings provide theoretical reference for deep understanding of quantum scattering properties and tuning resonances for high partial waves.