Freezing and Shielding under Global Quenches for Long-Range Interacting Many-Body Systems

TL;DR

This paper studies how long-range interactions in a many-body system can lead to dynamical freezing and shielding effects, especially after a sudden quench, revealing a universal feature linked to quasi-stationary states.

Contribution

It introduces the concept of shielding and freezing in long-range interacting systems and demonstrates their universality and relation to quasi-stationary states.

Findings

Freezing occurs when low energy gaps prevent mode mixing.

States within excited subspace are shielded from long-range effects.

Shielding and freezing are universal features in long-range systems.

Abstract

We investigate the time evolution of a Fermi-Hubbard model with long range hopping following a sudden quench of the local interactions among different spin species. The quasi-particle spectrum consists of gapped low-energy levels while the high energy modes accumulate at a single point. When the low energy gaps are large enough, turning on the local interactions does not effectively mix high and low energy modes, leading to the freezing of the dynamical evolution. In general, the states within the excited subspace are shielded from the long-range signatures of the model, which are responsible for the low energy extended states, and the dynamics effectively look as if long-range hopping were absent. This cooperative shielding mechanism becomes evident in presence of disorder. It is shown that shielding and freezing are a universal feature of long-range interacting systems and conjecture that they are related to the existence of quasi-stationary states.