Dresden 2017 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 62: Correlated Electrons: Nonequilibrium Quantum Many-Body Systems 1
TT 62.11: Vortrag
Donnerstag, 23. März 2017, 12:30–12:45, HSZ 304
Density propagator for many-body localization: finite size effects, transient subdiffusion, (stretched-)exponentials — •Soumya Bera1, Giuseppe De Tomasi1, Felix Weiner2, and Ferdinand Evers2 — 1MPI-PKS, Dresden — 2Institute of Theoretical Physics, University of Regensburg
We investigate charge relaxation in the spin-less disordered fermionic Hubbard chain (t−V-model). Our observable is the time-dependent density propagator, Πε(x,t), calculated in windows of different energy density, ε, of the many-body Hamiltonian and at different disorder strengths, W, not exceeding the critical value Wc. The width Δ xε(t) of Πε(x,t) exhibits a behavior dlnΔ xε(t) / dlnt = βε(t), where the exponent function βε(t)1/2 is seen to depend strongly on L at all investigated parameter combinations. (i) We confirm the existence of a region in phase space that exhibits subdiffusive dynamics in the sense that βε(t)<1/2 in large window of times. However, subdiffusion might possibly be transient, only, finally giving way to a conventional diffusive behavior with βε=1/2. (ii) We cannot confirm the existence of many-body mobility edges deep in the delocalized phase. (iii) (Transient) subdiffusion 0<βε(t) 1/2, coexists with an enhanced probability for returning to the origin, Πε(0,t), decaying much slower than 1/Δ xε(t). Correspondingly, the spatial decay of Πε(x,t) is far from Gaussian being exponential or even slower. On a phenomenological level, our findings are broadly consistent with effects of strong disorder and (fractal) Griffiths regions.