Antiferromagnetic magnons as highly squeezed Fock states underlying quantum correlations

Anno: 2019

Autori: Kamra A., Thingstad E., Rastelli G., Duine Rembert A., Brataas A., Belzig W., Sudbsh A.

Affiliazione autori: Norwegian Univ Sci & Technol, Dept Phys, Ctr Quantum Spintron, NO-7491 Trondheim, Norway. Univ Konstanz, Dept Phys, D-78457 Constance, Germany. Univ Konstanz, Zukunftskolleg, D-78457 Constance, Germany. Univ Utrecht, Inst Theoret Phys, NL-3584 CC Utrecht, Netherlands. Eindhoven Univ Technol, Dept Appl Phys, Eindhoven, Netherlands.

Abstract: Employing the concept of two-mode squeezed states from quantum optics, we demonstrate a revealing physical picture for the antiferromagnetic ground state and excitations. Superimposed on a Nyel ordered configuration, a spin-flip restricted to one of the sublattices is called a sublattice magnon. We show that an antiferromagnetic spin-up magnon is composed of a quantum superposition of states with n+1 spin-up and n spin-down sublattice magnons and is thus an enormous excitation despite its unit net spin. Consequently, its large sublattice spin can amplify its coupling to other excitations. Employing von Neumann entropy as a measure, we show that the antiferromagnetic eigenmodes manifest a high degree of entanglement between the two sublattices, thereby establishing antiferromagnets as reservoirs for strong quantum correlations. Based on these insights, we outline strategies for exploiting the strong quantum character of antiferromagnetic (squeezed) magnons and give an intuitive explanation for recent experimental and theoretical findings in antiferromagnetic magnon spintronics.

Giornale/Rivista: PHYSICAL REVIEW B

Volume: 100 (17)      Da Pagina: 174407  A: 174407

Maggiori informazioni: A.K. thanks S. Takei, L. Liensberger, M. Weiler, and H. Huebl for valuable discussions. We acknowledge financial support from the Research Council of Norway through its Centers of Excellence funding scheme, Project No. 262633, “QuSpin,” and the DFG through SFB 767. A.S. also acknowledges support from the Research Council of Norway, Grant No. 250985, “Fundamentals of Low-dissipative Topological Matter.”
Parole chiavi: magnons, squeezing
DOI: 10.1103/PhysRevB.100.174407