3 years ago

Nonabelian magnonics in antiferromagnets.

Weichao Yu, Jiang Xiao, Ran Cheng, Matthew W. Daniels, Di Xiao

We present a semiclassical formalism for antiferromagnetic (AFM) magnonics which promotes the central ingredient of spin wave chirality, encoded in a quantity called magnonic isospin, to a first-class citizen of the theory. We use this formalism to unify results of interest from the field under a single chirality-centric formulation. Our main result is that the isospin is governed by unitary time evolution, through a Hamiltonian projected down from the full spin wave dynamics. Because isospin is SU(2)-valued, its dynamics on the Bloch sphere are precisely rotations - which, in general, do not commute. Consequently, the induced group of operations on AFM spin waves is nonabelian. This is a paradigmatic departure from ferromagnetic magnonics, which operates purely within the abelian group generated by spin wave phase and amplitude. Our investigation of this nonabelian magnonics in AFM insulators focuses on studying several simple gate operations. We close by presenting an implementation in a semiclassical AFM (that is, with dynamics governed merely by the Landau-Lifshitz equation) of the quantum Fourier transform - a prototype of the computational power that can be accessed through the isospin degree of freedom.

Publisher URL: http://arxiv.org/abs/1801.06535

DOI: arXiv:1801.06535v2

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