Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session T00: Poster Session III (1pm- 4pm CST)
Thursday, March 17, 2022
Room: McCormick Place Exhibit Hall F1
Abstract: T00.00015 : Observation of phase synchronization and alignment during free induction decay of quantum spins with Heisenberg interactions*
well-established phenomenon apart from a few equally well-established exceptions. Here we report the surprising
theoretical observation that integrable as well as non-integrable 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.
We highlight that this differs from spontaneous synchronization in quantum dissipative systems.
Here, we observe mutual synchronization of local spin directions in closed systems
under unitary time evolution. In our numerical simulations, we investigate the free induction decay (FID) of an ensemble of up to
N = 25 quantum spins with s = 1/2 each by solving the time-dependent Schrödinger equation numerically exactly.
Our findings are related to, but not fully explained by conservation laws of the system.
Even if we cannot provide a full understanding of the phenomenon, it is very robust
against for instance random fluctuations of the Heisenberg couplings and inhomogeneous magnetic fields.
The observed synchronization is independent of whether the interaction is ferro- or antiferromagnetic.
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 and since the fixed magnitude of individual classical spins effectively acts like additional N conservation laws.
*This work was supported by the Deutsche Forschungsgemeinschaft DFG 355031190 (FOR~2692); 397300368 (SCHN~615/25-1)).
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