Competing regimes of motion of 1D mobile impurities

Phys Rev Lett. 2014 Aug 15;113(7):070601. doi: 10.1103/PhysRevLett.113.070601. Epub 2014 Aug 14.


We show that a distinguishable mobile impurity inside a one-dimensional many-body state at zero temperature generally does not behave like a quasiparticle. Instead, both the impurity dynamics as well as the ground state of the bath are fundamentally transformed by a diverging number of zero-energy excitations being generated, leading to what we call infrared-dominated (ID) dynamics. Combining analytics and density matrix renormalization group numerics, we provide a general formula for the power law governing ID dynamics at zero momentum, discuss a threshold beyond which quasiparticle dynamics may occur again, and study the competition between the ID and quasiparticle universality classes at larger impurity momenta.