Quantum 2025 – wissenschaftliches Programm
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MON: Monday Contributed Sessions
MON 11: Quantum Transport I
MON 11.4: Vortrag
Montag, 8. September 2025, 15:00–15:15, ZHG104
Scaling of diffusion constants in perturbed easy-axis Heisenberg spin chains — •Markus Kraft1, Mariel Kempa1, Jiaozi Wang1, Sourav Nandy2, and Robin Steinigeweg1 — 1University of Osnabrück, Department of Mathematics/Computer Science/Physics, D-49076 Osnabrück, Germany — 2Max Planck Institute for the Physics of Complex Systems, D-01187 Dresden, Germany
Understanding the physics of the integrable spin-1/2 XXZ chain has witnessed substantial progress, due to the development and application of sophisticated analytical and numerical techniques. Since integrability is rather the exception than the rule, a crucial question is the change of infinite-temperature magnetization transport under integrability-breaking perturbations. This question includes the stability of superdiffusion at the isotropic point and the change of diffusion constants in the easy-axis regime. In our work, we study this change of diffusion constants by a variety of methods and cover both, linear response theory in the closed system and the Lindblad equation in the open system, where we throughout focus on periodic boundary conditions. In the closed system, we find evidence for a continuous change of diffusion constants over the full range of perturbation strengths. In the open system weakly coupled to baths, we find diffusion constants in quantitative agreement with the ones in the closed system in a range of nonweak perturbations, but disagreement in the limit of weak perturbations. Using a simple model in this limit, we point out the possibility of a diverging diffusion constant in such an open system.
Keywords: Quantum transport; Nonequilibrium statistical mechanics; Heisenberg model; Integrable systems; Open quantum systems