Quantum-torque-induced breaking of magnetic interfaces in ultracold gases

Year: 2021

Authors: Farolfi A., Zenesini A., Trypogeorgos D., Mordini C., Gallemi A., Roy A., Recati A., Lamporesi G., Ferrari G.

Autors Affiliation: Univ Trento, INO CNR BEC Ctr, Dipartimento Fis, Povo, Italy; Ist Nazl Fis Nucl, Trento Inst Fundamental Phys & Applicat, Povo, Italy; CNR Nanotec, Inst Nanotechnol, Lecce, Italy; Swiss Fed Inst Technol, Inst Quantum Elect, Zurich, Switzerland

Abstract: A rich variety of physical effects in spin dynamics arise at the interface between different magnetic materials. Engineered systems with interlaced magnetic structures have been used to implement spin transistors, memories and other spintronic devices. However, experiments in solid-state systems can be difficult to interpret because of disorder and losses. Here we realize analogues of magnetic junctions using a coher- ently coupled mixture of ultracold bosonic gases. The spatial inhomogeneity of the atomic gas makes the system change its behaviour from regions with oscillating magnetization—resembling a magnetic material in the presence of an external transverse field—to regions with a defined magnetization, similar to magnetic materials with ferromagnetic anisotropy stronger than external fields. Starting from a far-from-equilibrium fully polarized state, magnetic inter- faces rapidly form. At the interfaces, we observe the formation of short-wavelength magnetic waves. They are generated by a quantum torque contribution to the spin current and pro- duce strong spatial anticorrelations in the magnetization. Our results establish ultracold gases as a platform for the study of far-from-equilibrium spin dynamics in regimes that are not easily accessible in solid-state systems.

Journal/Review: NATURE PHYSICS

Volume: 17 (12)      Pages from: 1359  to: 1363

More Information: We thank F. Dalfovo for his critical reading of the manuscript and M. Oberthaler, G. Consolo, D. Go, E. Mendive-Tapia and N. Pavloff for fruitful discussions. We acknowledge funding from INFN through the FISH project, from the European Union´s Horizon 2020 Programme through the NAQUAS project of QuantERA ERA-NET Cofund in Quantum Technologies (grant agreement no. 731473) and from Provincia Autonoma di Trento. We thank the BEC Center, the Q@TN initiative and QuTiP.
KeyWords: spin dynamics, magnetism, two-component condensate, ferromagnetism, coherent coupling
DOI: 10.1038/s41567-021-01369-y

Citations: 8
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