Tuneable electron-magnon coupling of ferromagnetic surface states in PdCoO2

Federico Mazzola*, Chi-Ming Yim, Veronika Sunko, Seunghyun Khim, Pallavi Kushwaha, Oliver J. Clark, Lewis Bawden, Igor Marković, Dibyashree Chakraborti, Timur K. Kim, Moritz Hoesch, Andrew P. Mackenzie, Peter Wahl, Philip D. C. King*

*Corresponding author for this work

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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 PdCoO2, 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.
Original languageEnglish
Article number20
Number of pages6
Journalnpj Quantum Materials
Volume7
DOIs
Publication statusPublished - 11 Feb 2022

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