Patterns resulted from modulation instability are ubiquitous and have been extensively studied in optics and Bose-Einstein condensates. However, these patterns have not been realized in ultracold Fermi gases, although there has been considerable theoretical interest in this field. Here we report an experimental observation of space-time patterns in a superfluid Fermi gas excited by red-detuned laser light. Longitudinal spatially fluctuated laser beams induce the spontaneous formation of two different kinds of patterns. For strongly interacting Fermi gas, the induced patterns accompanied by phonon excitations demonstrate a striking “X”-type dispersion relation between frequency and wavevector. Then, the propagation of such patterns in the Bose-Einstein condensate to Bardeen-Cooper-Schrieffer crossover is investigated, which is related to the speed of sound and agrees well with theoretical calculations. The observed patterns in noninteracting Fermi gases are stationary without phonon excitations and show a much longer lifetime.

调制不稳定性导致的模式无处不在，并已在光学和玻色-爱因斯坦凝聚中得到广泛研究。然而，这些模式尚未在超冷费米气体中实现，尽管该领域有相当大的理论兴趣。在这里，我们报告了对红色失谐激光激发的超流体费米气体中时空模式的实验观察。纵向空间波动的激光束诱导两种不同类型图案的自发形成。对于强相互作用的费米气体，伴随声子激发的诱导模式表明频率和波矢之间存在显着的“X”型色散关系。然后，研究了这种模式在 Bose-Einstein 凝聚中的传播到 Bardeen-Cooper-Schrieffer 交叉，这与声速有关，与理论计算非常吻合。在非相互作用的费米气体中观察到的模式在没有声子激发的情况下是静止的，并且显示出更长的寿命。