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DY: Fachverband Dynamik und Statistische Physik
DY 5: Many-body Systems: Equilibration, Chaos and Localization I (joint session DY/TT)
DY 5.7: Vortrag
Montag, 16. März 2020, 11:45–12:00, HÜL 186
Decay of spin-spin correlations in disordered quantum and classical spin chains — •Dennis Schubert, Jonas Richter, and Robin Steinigeweg — University of Osnabrück, Germany
The real-time dynamics of equal-site correlation functions is studied
for one-dimensional spin models with quenched disorder. Focusing on
infinite temperature, we present a comparison between the dynamics
of models with different quantum numbers s = 1/2, 1, 3/2 , as well as
of chains consisting of classical spins. Based on this comparison as well
as by analysing the statistics of energy-level spacings, we show that the
putative many-body localization transition is shifted to considerably
stronger values of disorder for increasing s . In this context, we intro-
duce an effective disorder strength, which provides a mapping between
the dynamics for different spin quantum numbers. For small values of
the effective disorder, we show that the real-time correlations become
essentially independent of s , and are moreover very well captured by
the dynamics of classical spins. Particularly for s = 3/2 , the agreement
between quantum and classical dynamics is remarkably observed even
for very strong values of disorder. This behaviour also reflects itself in
the appropriate spectral functions, which are obtained via a Fourier
transform from the time to the frequency domain. As an aside, we also
comment on the self-averaging properties of the correlation function at
weak and strong disorder.
[1] arXiv:1911.09917