Magnetization-induced dynamics of a Josephson junction coupled to a nanomagnet

Roopayan Ghosh; Moitri Maiti; Yury M. Shukrinov; K. Sengupta

doi:10.1103/PhysRevB.96.174517

← Back to search

Magnetization-induced dynamics of a Josephson junction coupled to a nanomagnet

Roopayan Ghosh, Moitri Maiti, Yury M. Shukrinov, K. Sengupta

DOI 10.1103/PhysRevB.96.174517 · Physical Review B

T1

Active bibliographic source — not scientific approval

Bibliographic access preserves source history; it does not approve extracted materials or validate reported claims. Review warnings on each occurrence separately.

Abstract

We study the superconducting current of a Josephson junction (JJ) coupled to an external nanomagnet driven by a time-dependent magnetic field both without and in the presence of an external ac drive. We provide an analytic, albeit perturbative, solution for the Landau-Lifshitz (LL) equations governing the coupled JJ-nanomagnet system in the presence of a magnetic field with arbitrary time dependence oriented along the easy axis of the nanomagnet's magnetization and in the limit of weak dimensionless coupling ε0 between the JJ and the nanomagnet. We show the existence of Shapiro-type steps in the I−V characteristics of the JJ subjected to a voltage bias for a constant or periodically varying magnetic field and explore the effect of rotation of the magnetic field and the presence of an external ac drive on these steps. We support our analytic results with exact numerical solution of the LL equations. We also extend our results to dissipative nanomagnets by providing a perturbative solution to the Landau-Lifshitz-Gilbert (LLG) equations for weak dissipation. We study the fate of magnetization-induced Shapiro steps in the presence of dissipation both from our analytical results and via numerical solution of the coupled LLG equations. We discuss experiments which can test our theory.