SKM 2021 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 4: Poster Session II: Nonlinear Dynamics, Simulations and Machine Learning
DY 4.4: Poster
Dienstag, 28. September 2021, 17:30–19:30, P
Observation of phase synchronization and alignment during free induction decay of quantum spins with Heisenberg interactions — •Patrick Vorndamme1, Heinz-Jürgen Schmidt2, Christian Schröder1,3, and Jürgen Schnack1 — 1Bielefeld University, 33615 Bielefeld, Germany — 2Osnabrück University, Barbarastraße 7, 49076 Osnabrück, Germany — 3Bielefeld Institute for Applied Materials Research, 33619 Bielefeld, Germany
Equilibration of observables in closed quantum systems that are described by a unitary time evolution is a meanwhile well-established phenomenon. Here we report the surprising theoretical observation that spin rings with nearest-neighbor or long-range isotropic Heisenberg interaction not only equilibrate but moreover also synchronize the directions of the expectation values of the individual spins. Here, we observe mutual synchronization of local spin directions in closed systems under unitary time evolution. This synchronization is independent of whether the interaction is ferro- or antiferromagnetic. In our numerical simulations, we investigate the free induction decay of an ensemble of quantum spins by solving the time-dependent Schrödinger equation numerically exactly. The synchronization is very robust against for instance random fluctuations of the Heisenberg couplings and inhomogeneous magnetic fields. Synchronization is not observed with strong enough symmetry-breaking interactions such as the dipolar interaction. We also compare our results to closed-system classical spin dynamics which does not exhibit phase synchronization due to the lack of entanglement. (arxiv:2104.05748)