title: Many-Body Localization Characterized from a One-Particle Perspective.
abstract: We show that the one-particle density matrix ρ can be used to characterize the interaction-driven many-body localization transition in closed fermionic systems. The natural orbitals (the eigenstates of ρ) are localized in the many-body localized phase and spread out when one enters the delocalized phase, while the occupation spectrum (the set of eigenvalues of ρ) reveals the distinctive Fock-space structure of the many-body eigenstates, exhibiting a steplike discontinuity in the localized phase. The associated one-particle occupation entropy is small in the localized phase and large in the delocalized phase, with diverging fluctuations at the transition. We analyze the inverse participation ratio of the natural orbitals and find that it is independent of system size in the localized phase.
authors.affiliation: Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany.
authors.forename: Soumya
authors.initials: S
authors.lastname: Bera
authors.affiliation: Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany.|Department of Physics, Lancaster University, LA1 4YB Lancaster, United Kingdom.
authors.forename: Henning
authors.initials: H
authors.lastname: Schomerus
authors.affiliation: Department of Physics and Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universität München, 80333 München, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Heidrich-Meisner
authors.affiliation: Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany.
authors.forename: Jens H
authors.initials: JH
authors.lastname: Bardarson