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SUMMARY:Many-Body Localization Characterized from a One-Particle Perspecti
 ve - Fabian Heidrich-Meisner (LMU)
DTSTART:20160125T153000Z
DTEND:20160125T170000Z
UID:TALK63224@talks.cam.ac.uk
CONTACT:6270
DESCRIPTION:Many-body localization (MBL) is the disorder-driven perfect in
 sulating behavior of a generic interacting lattice system of local charge 
 or spin degrees of freedom. This state of matter is an insulator at finite
  energy densities\, fails to thermalize and violates the eigenstate therma
 lization hypothesis\, and many-body eigenstates exhibit an area law instea
 d of a volume law typical for thermal states. The MBL phase is separated f
 rom an ergodic disordered phase by a localization-delocalization transitio
 n that has no signatures in thermodynamics but in dynamical properties.\n\
 nWe here show that the eigenstates and the spectrum of the one-particle de
 nsity matrix (OPDM) can be used to characterize the interaction-driven man
 y-body localization transition in closed fermionic systems. The natural or
 bitals (the eigenstates of OPDM) are localized in the many-body localized 
 phase and spread out when one enters the delocalized phase The natural orb
 itals are single-particle states and share many properties with the single
 -particle eigenstates of an Anderson insulator. In particular\, they posse
 ss exponentially decaying tails in the MBL phase.\nThe occupation spectrum
  (the set of eigenvalues of OPDM) reveals the distinctive Fock-space struc
 ture of the many-body eigenstates\, exhibiting a steplike discontinuity in
  the localized phase. This existence discontinuity implies a close analogy
  between the MBL phase and a zero-temperature Fermi liquid: Both systems p
 ossess long-lived quasi-particles\, are integrable and thus do not thermal
 ize and many-body eigenstates are only weakly spread out in Fock space. We
  frame our results into the existing theory of the MBL phase and in partic
 ular make a connection to the emergent quasi-local conserved charges that 
 exist in the MBL phase\n
LOCATION:Ryle Seminar (Rutherford 930)
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