| The ultracold gases have become an ideal research platform for their accuracy and controllability,and have wide applications in precision measurement,quantum simulation,quantum information,and so on.In much related work,how to effectively modulate the atom-atom interaction is the key to achieving breakthrough results,and Feshbach resonance provides technical support.There are two kinds of Feshbach resonance,magnetic Feshbach resonance(MFR)and optical Feshbach resonance(OFR),the former uses magnetic field for modulation and the latter uses optical field.The advantage of OFR is that it can achieve spatiotemporal modulation of atomatom interaction,and OFR modulation on the submicron scale has been successfully achieved in experiment.However,the numerical value of the optical length fitted in the experiment is inconsistent with the theoretical value(Phys.Rev.Lett.105,050405(2010)).MFR is widely used in precision measurement due to its advantages such as uniform spatial regulation and less atomic loss.While using MFR to adjust the atomatom interaction to zero,more than 20000 Bloch oscillations have been successfully observed in optical lattices,but this experiment has observed decoherence phenomena which is inconsistent with theory(Phys.Rev.Lett.100,080404(2008)).We conduct a theoretical study on the discrepancy between theory and experiment in the research of matter-wave optics associated with Feshbach resonance.In previous theoretical studies,the local field effect(LFE)of the ultracold gases was neglected.LFE refers to the feedback of the ultracold gases as a quantum dielectric material on the propagation of the optical field,resulting in changes of the optical lattice structure.LFE can be used to study new physical effects,such as self-bound quantum droplets,self-accelerating matter wave solitons,and spontaneous crystallization of atoms and light.So far,LFE has not been considered in the study of matter-wave optics associated with Feshbach resonance.Therefore,in this paper,we combine LFE and the matter wave optics regulated by Feshbach resonance,and explain the discrepancy between theoretical and experimental results in submicron scale OFR experiment and Bloch oscillation experiment regulated by MFR.We have obtained the following innovative results:(1)In the OFR modulation of the submicron scale considering LFE,we find that the atomic losses induced by stimulated radiation of the molecular state can be reduced by LFE,especially in the red detuning region of molecular resonance,where they are significantly reduced.Besides,we can use Green function and Born approximation to show that LFE can produce effective long-range many-body interaction,beyond twobody short-range interaction,when coupling to the molecular transition during OFR.Finally,our analysis shows that LFE is an important factor contributing to the discrepancy between theory and experiment in OFR experiments at the submicron spatial scale,and the combination of LFE and OFR is a new method for producing beyond two-body long-range interactions.(2)We investigate Bloch oscillations in optical lattices regulated by MFR and find that LFE induces an equivalent atom-atom interaction.We demonstrate through theoretical analysis and numerical calculations that this equivalent atom-atom interaction can lead to the decoherence of Bloch oscillations in the optical lattice.In addition,the equivalent atom-atom interaction caused by LFE generally behaves as attractive potential.Therefore,when the actual interaction between atoms is attractive(repulsive),LFE will exacerbate(alleviate)the decoherence effect.Even if the interatomic interaction can be ignored,LFE will bring about the quantum decoherence effect,which can bring new theoretical explanations to some experiments and pose a higher challenge to the field of precision measurement. |
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