Asymmetric matter-wave diffraction in a forced harmonic potential

Abstract

Matter-wave diffraction is an important and widely used method for manipulating atomic momentum states and for studying dynamical evolution in ultracold-atom physics. Here, we investigated momentum diffraction of ultracold 87Rb atoms using a short lattice pulse in the presence of a forced harmonic potential. The forced potential is achieved by combining a magnetic field gradient and a crossed-dipole trap. By tuning the gradient field strength and atomic evolution time in the trap, we found that populations of the forward and backward diffractive momentum components exhibit asymmetry relative to the original matter wave, a feature that has often been overlooked or deliberately avoided in previous studies. The factors that induce this asymmetric diffraction are identified and systematically analyzed, including the initial atomic velocity, the trap potential gradient, and the cooperative interactions among atomic spin-momentum modes. A transparent physical picture supported by analytical modeling is presented. This work can provide a better understanding of matter-wave diffraction in the presence of external fields and in complex or imperfect lattice configurations, thereby potentially advancing future research on ultracold atom interferometry and quantum simulation involving multiple spin-momentum modes.