Twin peaks and boomerang in quantum-chaotic systems*

We investigate the build-up of a twin-peak structure in the momentum distribution of a quantum wavepacket launched in a quantum-chaotic system. While this phenomenon has been originally associated with the Anderson localization in a disordered potential landscape, our study reveals that it is a more common feature of quantum chaos. In particular, we have put forward a general theoretical framework for the twin peaks as the combined effects of system boundedness and chaos, even emerging in the absence of the time-reversal symmetry. Furthermore, we show that the quantum boomerang is the real-space sibling of the twin peaks in the momentum space.