Persistent-current states originating from the Hilbert space fragmentation in momentum space

TL;DR

This paper demonstrates how Hilbert space fragmentation in momentum space leads to persistent-current states and analyzes their stability against disorder, revealing decay rates independent of current velocity.

Contribution

It constructs a Hamiltonian exhibiting Hilbert space fragmentation in momentum space and shows the emergence and stability of persistent-current states within this framework.

Findings

Persistent-current states arise from Hilbert space fragmentation in momentum space.

Decay rate of persistent-current states is nearly independent of current velocity.

Stability of these states is tested against random potential, showing robustness.

Abstract

Hilbert space fragmentation (HSF) is a phenomenon that the Hilbert space of an isolated quantum system splits into exponentially many disconnected subsectors. The fragmented systems do not thermalize after long-time evolution because the dynamics are restricted to a small subsector. Inspired by recent developments of the HSF, we construct the Hamiltonian that exhibits the HSF in the momentum space. We show that persistent-current (PC) states emerge due to the HSF in the momentum space. We also investigate the stability of the PC states against the random potential, which breaks the structure of the HSF, and find that the decay rate of the PC is almost independent of the current velocity.