Quantum flutter of supersonic particles in one-dimensional quantum liquids

Fast obstacles in a medium are responsible for striking physical phenomena, such as aerodynamic flutter, Cerenkov radiation and acoustic shock waves. In a hydrodynamic picture, quantum systems exhibit analogues of these dynamical features. Here we uncover novel quantum dynamics induced by fast particles by considering impurities injected supersonically into a one-dimensional quantum liquid. We find that the injected particle never comes to a full stop, at odds with conventional expectations of relaxation. Furthermore the system excites a new type of collective mode, manifesting itself in several observable quantities, such as long-lived oscillations in the velocity of the injected particle and simultaneous oscillations of the correlation hole formed around the impurity. These features are inherently quantum-mechanical and provide an example of a dynamically formed quantum coherent state propagating through a many-body environment while maintaining its coherence. The signatures of these effects can be probed directly with existing experimental tools.