Entanglement and diagonal entropies after a quench with no pair structure

Understand

A typical working condition in the study of quantum quenches is that the initial state produces a distribution of quasiparticle excitations with an opposite-momentum-pair structure.

• In this work we investigate the dynamical and stationary properties of the entanglement entropy after a quench from initial states which do not have such structure: instead of pairs of excitations they generate $\nu$-plets of correlated excitations with $\nu>2$.
• Our study is carried out focusing on a system of non-interacting fermions on the lattice.
• We study the time evolution of the entanglement entropy showing that the standard semiclassical formula is not applicable.