Superluminal moving defects in the Ising spin chain

Understand

Quantum excitations in lattice systems always propagate at a finite maximum velocity.

• We probe this mechanism by considering a defect travelling at a constant velocity in the quantum Ising spin chain in transverse field.
• Independently of the microscopic details of the defect, we characterize the expectation value of local observables at large times and large distances from the impurity, where a Local Quasi Stationary State (LQSS) emerges.
• The LQSS is strongly affected by the defect velocity: for superluminal defects, it exhibits a growing region where translational invariance is spontaneously restored.