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Quantum Stoner-Wohlfarth Model

Phys. Rev. Lett. 116, 037203

2016年1月22日(金)

Takuya Hatomura, Bernard Barbara, and Seiji Miyashita ( https://doi.org/10.1103/PhysRevLett.116.037203 )

Abstract

The quantum mechanical counterpart of the famous Stoner-Wohlfarth model—an easy-axis magnet in a tilted magnetic field—is studied theoretically and through simulations as a function of the spin size S in a sweeping longitudinal field. Beyond the classical Stoner-Wohlfarth transition, the sweeping field-induced adiabatic change of states slows down as S increases, leading to a dynamical quantum phase transition. This result gives us new insights to describe the collapse of the metastability from the viewpoint of a critical phenomenon associated with the Landau-Zener tunneling gaps. Furthermore, a beating of the amplitude of the magnetization (the spin-length fidelity) is discovered after the Stoner-Wohlfarth transition. The period of the beating, confirmed analytically, arises from a new type of quantum phase factor.

その他特記事項

The present work was supported by Grants-in-Aid for Scientific Research C (Grant No. 25400391) from MEXTof Japan, and the Elements Strategy Initiative Center for Magnetic Materials under the outsourcing project of MEXT. The numerical calculations were supported by the supercomputer center of ISSP of the University of Tokyo.
T. H. is supported by the Program for Leading Graduate Schools: Material Education program for the future leaders in Research, Industry, and Technology (MERIT) from JSPS, and the JSPS Core-to-Core Program: Nonequilibrium dynamics of soft matter and information.


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