Abstract

We consider synchronization properties of arrays of spin-torque nano-oscillators coupled via an RC load. We show that while the fully synchronized state of identical oscillators may be locally stable in some parameter range, this synchrony is not globally attracting. Instead, regimes of different levels of compositional complexity are observed. These include chimera states (a part of the array forms a cluster while other units are desynchronized), clustered chimeras (several clusters plus desynchronized oscillators), cluster state (all oscillators form several clusters), and partial synchronization (no clusters but a nonvanishing mean field). Dynamically, these states are also complex, demonstrating irregular and close to quasiperiodic modulation. Remarkably, when heterogeneity of spin-torque oscillators is taken into account, dynamical complexity even increases: close to the onset of a macroscopic mean field, the dynamics of this field is rather irregular.

Highlights

  • Synchronization in large populations of self-sustained periodic oscillators occurs in many physical, biological, engineering and social systems, see recent reviews[1, 2]

  • Our results show that these oscillators, being more complex than the phase oscillators used in many studies, demonstrate more complex properties of the collective dynamics

  • The coupling is due to the giant magnetic resistance (GMR) effect, as the resistance of an spin-torque oscillators (STOs) depends on the orientation of its magnetization, so that the redistribution of the ac current between the STO array and the load depends on the the average value of this resistance

Read more

Summary

Introduction

Synchronization in large populations of self-sustained periodic oscillators occurs in many physical, biological, engineering and social systems, see recent reviews[1, 2]. Even for identical oscillators under global (mean field) coupling, complex synchronization regimes like partial synchrony10–12, “chimera“s13–15, heteroclinic cycles[16] have been reported For many such regimes it is still not clear, how robust they are, and whether different dynamic states can coexist. The coupling is due to the giant magnetic resistance (GMR) effect, as the resistance of an STO depends on the orientation of its magnetization, so that the redistribution of the ac current between the STO array and the load depends on the the average (over the array) value of this resistance This setup corresponds to the general scheme of mean-field coupling, as discussed above. The mean field appears to be highly irregular in a large range of parameters, making the transition to synchrony in this ensemble quite different from the usual transitions observed, e. g., in the Kuramoto model

Methods
Results
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call