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TT: Fachverband Tiefe Temperaturen

TT 9: Many-body Systems: Equilibration, Chaos and Localization I (joint session DY/TT)

TT 9.7: 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