Nonthermalized dynamics of flat-band many-body localization

We find that a flat-band fermion system with interactions and without disorders exhibits nonthermalized ergodicity-breaking dynamics, an analog of many-body localization (MBL). In the previous works we observed flat-band many-body localization (FMBL) in the Creutz ladder model. The origin of FMBL is a compact localized state governed by local integrals of motion (LIOMs), which are to be obtained explicitly. In this work we clarify the dynamical aspects of FMBL. We first study dynamics of two particles, and find that the states are not substantially modified by weak interactions, but the periodic time evolution of entanglement entropy emerges as a result of a specific mechanism inherent in the system. On the other hand, as the strength of the interactions is increased, the modification of the states takes place with inducing instability of the LIOMs. Furthermore, many-body dynamics of the system at finite fillings is numerically investigated by the time-evolving block decimation (TEBD) method. For a suitable choice of the filling, nonthermal and low entangled dynamics appears. This behavior is a typical example of the disorder-free FMBL.

Automated summary

The study reveals that a flat-band fermion system with interactions but without disorders exhibits nonthermalized ergodicity-breaking dynamics, similar to many-body localization (MBL). The dynamics of two particles show that the modification of states is influenced by the strength of interactions, leading to instability of local integrals of motion (LIOMs). Numerical investigation of many-body dynamics at finite fillings using the time-evolving block decimation (TEBD) method demonstrates nonthermal and low entangled dynamics, a characteristic of disorder-free flat-band many-body localization (FMBL).