Stable solitons in a nearly PT-symmetric ferromagnet with spin-transfer torque

PHYSICA D-NONLINEAR PHENOMENA

卷:409

Article

Barashenkov, I., V^1,2  Chernyavsky, Alexander^1,3 

[1] Univ Cape Town, Ctr Theoret & Math Phys, ZA-7701 Rondebosch, South Africa

[2] Joint Inst Nucl Res, Dubna 141980, Russia

[3] Univ Victoria, Dept Math & Stat, Victoria, BC V8P 5C2, Canada

关键词: Spin torque oscillator;    Landau-Lifshitz equation;    Parity-time symmetry;    Nonlinear Schroedinger equation;    Solitons;    Stability;   

DOI  :  10.1016/j.physd.2020.132481

来源: Elsevier

【 摘 要 】

We consider the Landau-Lifshitz equation for the spin torque oscillator - a uniaxial ferromagnet in an external magnetic field with polarised spin current driven through it. In the absence of the Gilbert damping, the equation turns out to be PT-symmetric. We interpret the PT-symmetry as a balance between gain and loss - and identify the gaining and losing modes. In the vicinity of the bifurcation point of a uniform static state of magnetisation, the PT-symmetric Landau-Lifshitz equation with a small dissipative perturbation reduces to a nonlinear Schrodinger equation with a quadratic nonlinearity. The analysis of the Schrodinger dynamics demonstrates that the spin torque oscillator supports stable magnetic solitons. The PT near-symmetry is crucial for the soliton stability: the addition of a finite dissipative term to the Landau-Lifshitz equation destabilises all solitons that we have found. (C) 2020 Elsevier B.V. All rights reserved.

【 授权许可】

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