磁斯格明子是一種具有準(zhǔn)粒子特性的磁渦旋結(jié)構(gòu)，有望成為新型自旋電子學(xué)器件的信息載體。其中，基于斯格明子的納米振蕩器因其在微波通信和神經(jīng)形態(tài)計(jì)算中的應(yīng)用潛力而備受關(guān)注。此前的研究主要集中于單個(gè)斯格明子振蕩器，其輸出功率和執(zhí)行的功能有限，難以滿(mǎn)足實(shí)際應(yīng)用的需要。

一種可能的解決方案是構(gòu)建由耦合振蕩器組成的網(wǎng)絡(luò)，通過(guò)振蕩器之間的非線(xiàn)性效應(yīng)實(shí)現(xiàn)信號(hào)放大。最近研究發(fā)現(xiàn)，亞鐵磁斯格明子振蕩器具有可擴(kuò)展優(yōu)勢(shì)，為振蕩器之間的非線(xiàn)性物理研究提供了條件。然而，相互耦合的亞鐵磁斯格明子振蕩器的具體動(dòng)力學(xué)行為及其可調(diào)控性尚不清楚。

Fig. 2 Frequency spectra for different oscillator spacings.

來(lái)自北京師范大學(xué)物理學(xué)系高等量子研究中心的沈卡教授團(tuán)隊(duì)，利用微磁模擬和有效動(dòng)力學(xué)方程求解，研究了相互作用亞鐵磁斯格明子振蕩器的動(dòng)力學(xué)行為，證明了不同振蕩器中斯格明子運(yùn)動(dòng)的同步、頻率梳等非線(xiàn)性效應(yīng)。

他們的研究表明：當(dāng)振蕩器之間耦合較弱時(shí)，振蕩器彼此獨(dú)立；隨著耦合增強(qiáng)，系統(tǒng)的頻譜出現(xiàn)等間距的峰，實(shí)現(xiàn)頻率梳特征；隨著耦合進(jìn)一步增強(qiáng)至某一臨界值以上，不同振蕩器中的斯格明子以相同的頻率振蕩，進(jìn)入同步態(tài)。

作者發(fā)現(xiàn)，從頻率梳到同步態(tài)的轉(zhuǎn)變與斯格明子間的有效勢(shì)能在不同耦合強(qiáng)度下的演化有關(guān)。該研究不僅證明了亞鐵磁斯格明子振蕩器在非線(xiàn)性物理研究中的應(yīng)用，還揭示了其非線(xiàn)性動(dòng)力學(xué)背后的物理。該文近期發(fā)表于npj?Computational Materials?10:?48?(2024)。手機(jī)閱讀原文，請(qǐng)點(diǎn)擊本文底部左下角“閱讀原文”，進(jìn)入后亦可下載全文PDF文件。

Editorial Summary

Magnetic skyrmions, swirling magnetic textures with particle-like properties, are promising candidates as information carriers for advanced spintronic devices. In particular, skyrmion-based nano-oscillators have received much attention due to their potential applications in microwave communication and neuromorphic computing. Previous proposals are mainly based on single skyrmion oscillators, which lead to relatively low output power and limited functions and therefore are not suitable for practical applications. One solution is then to use the nonlinear effects in a network of coupled oscillators. Recent theoretical work demonstrated that boundary-free spin torque nano-oscillators based on ferrimagnetic skyrmions could be a suitable platform for studying nonlinear physics of coupled oscillators. However, the specific dynamical behaviors of such interacting oscillators as well as their tunability remain to be explored.

A team led by Prof. Ka Shen from the Center for Advanced Quantum Studies and Department of Physics, Beijing Normal University, China, investigated the dynamical behaviors of ferrimagnetic-skyrmion-based interacting oscillators through the micromagnetic simulation and the numerical solution of the effective kinetic equation. They demonstrated nonlinear effects of skyrmions in coupled oscillators, including synchronization and frequency comb. Their results showed that for a relatively weak coupling between the oscillators, the oscillators keep nearly individual. As the coupling strength increases, equally spaced discrete frequencies gradually appear in the Fourier spectrum of the dynamic quantities, corresponding to a frequency comb. Once the coupling strength exceeds a critical value, the skyrmions in different oscillators move at the same frequency, achieving a synchronization state. Moreover, the authors found that the transition from frequency comb to synchronization is related to the evolution of the effective potential energies of skyrmions under different coupling strengths. These findings not only demonstrate the potential application of ferrimagnetic-skyrmion-based oscillators in nonlinear physics research, but also reveal the underlying physics behind their nonlinear dynamics. Thisarticle was recently?published in?npj?Computational Materials?10:?48?(2024).

原文Abstract及其翻譯

Nonlinear dynamics of directly coupled skyrmions in ferrimagnetic spin torque nano-oscillators (亞鐵磁振蕩器中直接耦合的斯格明子非線(xiàn)性動(dòng)力學(xué))

Laichuan Shen,Lei Qiu?&?Ka Shen?

Abstract?Nonlinear spin torque nano-oscillators have received substantial attentions due to their important applications in microwave communication and neuromorphic computing. Here we investigate the dynamical behaviors of directly coupled skyrmion oscillators in a synthetic ferrimagnet. We demonstrate through the micromagnetic simulation and Thiele’s equation that the skyrmion oscillators can present either synchronization or frequency comb, depending on the strength of interactions between the skyrmions. The underlying physics of the transition between the two scenarios are unveiled based on a quantitative analysis of the effective potentials, which also successfully interprets the dependence of the transition on parameters. By further demonstrating the tunability of the nonlinear dynamics by the driving current of the oscillators, our work reveals the great potentials of ferrimagnetic-skyrmion-based interacting oscillators for nonlinear applications.

摘要由于在微波通信和神經(jīng)形態(tài)計(jì)算中的應(yīng)用前景，非線(xiàn)性自旋矩納米振蕩器受到廣泛關(guān)注。在本文中，我們研究了合成亞鐵磁中直接耦合的斯格明子振蕩器的動(dòng)力學(xué)行為。通過(guò)微磁模擬和Thiele方程求解，我們證明了振蕩器中的多個(gè)斯格明子在不同相互作用強(qiáng)度下可以實(shí)現(xiàn)同步或頻率梳。基于有效勢(shì)能的定量分析揭示了兩種動(dòng)力學(xué)之間轉(zhuǎn)變的物理本質(zhì)，并成功解釋了模擬中觀察到的參數(shù)依賴(lài)。進(jìn)一步，我們證明了驅(qū)動(dòng)電流對(duì)兩種非線(xiàn)性動(dòng)力學(xué)的調(diào)控。這些結(jié)果表明相互耦合的亞鐵磁斯格明子振蕩器在非線(xiàn)性應(yīng)用中的巨大潛力。