Dresden 2026 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 45: Many-body Systems: Equilibration, Chaos, and Localization (joint session DY/TT)
TT 45.3: Vortrag
Mittwoch, 11. März 2026, 10:00–10:15, HÜL/S186
Spin-Spin Correlations and Multifractality in 1D disordered SU(2)-Invariant Heisenberg Spin Chains — •Debasmita Giri, Julian Siegl, and John Schliemann — Institute for Theoretical Physics, University of Regensburg, Regensburg, Germany
Disorder and interactions in one-dimensional quantum spin chains give rise to rich non-ergodic phenomena that lie beyond the conventional eigenstate thermalization hypothesis (ETH). In the presence of sufficiently strong quenched disorder, many-body localization (MBL) can emerge: transport is frozen, entanglement growth is logarithmically slow, and local operators retain memory of their initial conditions even at infinite temperature. On the contrary, studies on models with non-Abelian symmetries have demonstrated that continuous symmetries, such as SU(2), can obstruct the construction of local integrals of motion and thus hinder full localization. We investigate spin correlations in one-dimensional SU(2)-invariant Heisenberg chains with exchange disorder for spin lengths S=1/2 and S=1. In the weak-disorder regime, the eigenmodes of the spin-spin correlation matrix are delocalized, consistent with ergodic behavior. Under strong disorder, the system enters a quasi-localized multifractal phase characterized by exponentially decaying, dimer-like spin correlations. Finite-size scaling of the inverse participation ratios of the correlation-matrix eigenmodes yields a correlation dimension, D2≈ 0.37−0.39, confirming the presence of a multifractal regime that is distinct from both the ergodic limit (D2=1) and the fully localized limit (D2=0).
Keywords: Multifractality; Disordered Heisenberg Spin Chains; Spin-spin correlation; Inverse participation Ratio