Tuneable electron-magnon coupling of ferromagnetic surface states in PdCoO${}_2$

Abstract

Controlling spin wave excitations in magnetic materials underpins the burgeoning field of magnonics. Yet, little is known about how magnons interact with the conduction electrons of itinerant magnets, or how this interplay can be controlled. Via a surface-sensitive spectroscopic approach, we demonstrate a strong and highly-tuneable electron-magnon coupling at the Pd-terminated surface of the delafossite oxide PdCoO${}_2$, where a polar surface charge mediates a Stoner transition to itinerant surface ferromagnetism. We show how the coupling can be enhanced 7-fold with increasing surface disorder, and concomitant charge carrier doping, becoming sufficiently strong to drive the system into a polaronic regime, accompanied by a significant quasiparticle mass enhancement. Our study thus sheds new light on electron-magnon interactions in solid-state materials, and the ways in which these can be controlled.

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Cited by in corpus (8)

• Metallic delafossite thin films for unique device applications
• Magnon Interference Tunneling Spectroscopy as a Probe of 2D Magnetism
• Avoided metallicity in a hole-doped Mott insulator on a triangular lattice
• Emergent magnetism with continuous control in the ultrahigh conductivity layered oxide PdCoO2
• Fully two-dimensional incommensurate charge modulation on the Pd-terminated polar surface of PdCoO2
• Adsorbate-induced formation of a surface-polarity-driven nonperiodic superstructure
• Disentangling Electron-Boson Interactions on the Surface of a Familiar Ferromagnet
• Dichotomy of electron-phonon interactions in the delafossite PdCoO${}_2$: From weak bulk to polaronic surface coupling