Many-body localization in the Fock space of natural orbitals

TL;DR

This paper investigates many-body localization in the Fock space of natural orbitals, revealing a sharp phase crossover and stronger localization compared to the computational basis, with implications for understanding localization phenomena.

Contribution

It introduces a novel analysis of many-body localization using natural orbital-based Fock basis, highlighting a phase crossover and basis-dependent localization strength.

Findings

Sharp crossover between phases near the onset of subdiffusive behavior

Eigenstates are more localized in the natural orbital Fock basis than in the computational basis

Localization properties depend strongly on the choice of basis

Abstract

We study the eigenstates of a paradigmatic model of many-body localization in the Fock basis constructed out of the natural orbitals. By numerically studying the participation ratio, we identify a sharp crossover between different phases at a disorder strength close to the disorder strength at which subdiffusive behaviour sets in, significantly below the many-body localization transition. We repeat the analysis in the conventionally used computational basis, and show that many-body localized eigenstates are much stronger localized in the Fock basis constructed out of the natural orbitals than in the computational basis.