Renormalization of antiferromagnetic magnons by superconducting condensate and quasiparticles

TL;DR

This paper explores how hybrid structures of antiferromagnetic insulators with superconductors or normal metals can be used to tune magnon dispersion through interface-induced exchange fields, enabling control without external magnetic fields.

Contribution

It introduces a method to modify magnon dispersion in antiferromagnetic insulators via interface exchange interactions with superconducting or normal metals, revealing a new way to engineer magnonic properties.

Findings

Magnon mode splitting occurs without external magnetic fields.

Interface exchange fields induce renormalization of magnon dispersion.

Measurement of dispersion can quantify the exchange field amplitude.

Abstract

The ability to modify and tune the spin-wave dispersion is one of the most important requirements for engineering of magnonic networks. In this study we demonstrate the promise of synthetic thin-film hybrids composed of an antiferromagnetic insulator (AF) and a normal (N) or superconducting (S) metal for tuning and modifying the spin-wave dispersion in antiferromagnetic insulators. The key ingredient is the uncompensated magnetic moment at the AF/S(N) interface, which induces an effective exchange field in the adjacent metal via the interface exchange interaction. The exchange field spin polarizes quasiparticles in the metal and induces spinful triplet Cooper pairs screening the magnon. The quasiparticle and Cooper pair polarization renormalizes the magnon dispersion. The renormalization results in the splitting of the otherwise degenerate AF magnon modes with no need to apply a magnetic field. It is also proposed that measurements of the renormalized dispersion relations can provide the amplitude of the effective exchange field induced by the AF in the adjacent metal.