Tuneable electron–magnon coupling of ferromagnetic surface states in PdCoO2

F. Mazzola; C. M. Yim; V. Sunko; S. Khim; P. Kushwaha; O. J. Clark; L. Bawden; I. Marković; D. Chakraborti; T. K. Kim; M. Hoesch; A. P. Mackenzie; P. Wahl; P. D.C. King

doi:10.1038/s41535-022-00428-8

Tuneable electron–magnon coupling of ferromagnetic surface states in PdCoO₂

F. Mazzola^*, C. M. Yim, V. Sunko, S. Khim, P. Kushwaha, O. J. Clark, L. Bawden, I. Marković, D. Chakraborti, T. K. Kim, M. Hoesch, A. P. Mackenzie, P. Wahl, P. D.C. King^*

^*Corresponding author for this work

Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

7 Citations (Scopus)

13 Downloads (Pure)

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 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 is enhanced sevenfold 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 light on electron–magnon interactions in solid-state materials, and the ways in which these can be controlled.

Original language	English
Article number	20
Number of pages	6
Journal	npj Quantum Materials
Volume	7
Issue number	1
DOIs	https://doi.org/10.1038/s41535-022-00428-8
Publication status	Published - 11 Feb 2022

Bibliographical note

Funding Information:
We thank C. Hooley, T. Frederiksen, G. van der Laan, G. Panaccione, H. Rosner and G. Siemann for useful discussions. We gratefully acknowledge support from the European Research Council (through the QUESTDO project, 714193), the Royal Society, the Max-Planck Society, and the UKRI Engineering and Physical Sciences Research Council (Grant No. EP/S005005/1). We thank Diamond Light Source for access to Beamline I05 (Proposals SI12469, SI14927, and SI16262), which contributed to the results presented here. V.S., O.J.C., and L.B. acknowledge the EPSRC for PhD studentship support through Grants EP/L015110/1, EP/K503162/1, and EP/G03673X/1, respectively. I.M. and D.C. acknowledge studentship support from the International Max-Planck Research School for Chemistry and Physics of Quantum Materials.

Publisher Copyright:
© 2022, The Author(s).

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Condensed Matter Physics

Access to Document

10.1038/s41535-022-00428-8Licence: Creative Commons: Attribution (CC BY)

MazzolaF2022Final published version, 2.11 MBLicence: Creative Commons: Attribution (CC BY)

Cite this

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title = "Tuneable electron–magnon coupling of ferromagnetic surface states in PdCoO2",

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 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 is enhanced sevenfold 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 light on electron–magnon interactions in solid-state materials, and the ways in which these can be controlled.",

author = "F. Mazzola and Yim, {C. M.} and V. Sunko and S. Khim and P. Kushwaha and Clark, {O. J.} and L. Bawden and I. Markovi{\'c} and D. Chakraborti and Kim, {T. K.} and M. Hoesch and Mackenzie, {A. P.} and P. Wahl and King, {P. D.C.}",

note = "Funding Information: We thank C. Hooley, T. Frederiksen, G. van der Laan, G. Panaccione, H. Rosner and G. Siemann for useful discussions. We gratefully acknowledge support from the European Research Council (through the QUESTDO project, 714193), the Royal Society, the Max-Planck Society, and the UKRI Engineering and Physical Sciences Research Council (Grant No. EP/S005005/1). We thank Diamond Light Source for access to Beamline I05 (Proposals SI12469, SI14927, and SI16262), which contributed to the results presented here. V.S., O.J.C., and L.B. acknowledge the EPSRC for PhD studentship support through Grants EP/L015110/1, EP/K503162/1, and EP/G03673X/1, respectively. I.M. and D.C. acknowledge studentship support from the International Max-Planck Research School for Chemistry and Physics of Quantum Materials. Publisher Copyright: {\textcopyright} 2022, The Author(s).",

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doi = "10.1038/s41535-022-00428-8",

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AU - Mazzola, F.

AU - Yim, C. M.

AU - Sunko, V.

AU - Khim, S.

AU - Kushwaha, P.

AU - Clark, O. J.

AU - Bawden, L.

AU - Marković, I.

AU - Chakraborti, D.

AU - Kim, T. K.

AU - Hoesch, M.

AU - Mackenzie, A. P.

AU - Wahl, P.

AU - King, P. D.C.

N1 - Funding Information: We thank C. Hooley, T. Frederiksen, G. van der Laan, G. Panaccione, H. Rosner and G. Siemann for useful discussions. We gratefully acknowledge support from the European Research Council (through the QUESTDO project, 714193), the Royal Society, the Max-Planck Society, and the UKRI Engineering and Physical Sciences Research Council (Grant No. EP/S005005/1). We thank Diamond Light Source for access to Beamline I05 (Proposals SI12469, SI14927, and SI16262), which contributed to the results presented here. V.S., O.J.C., and L.B. acknowledge the EPSRC for PhD studentship support through Grants EP/L015110/1, EP/K503162/1, and EP/G03673X/1, respectively. I.M. and D.C. acknowledge studentship support from the International Max-Planck Research School for Chemistry and Physics of Quantum Materials. Publisher Copyright: © 2022, The Author(s).

PY - 2022/2/11

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N2 - 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 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 is enhanced sevenfold 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 light on electron–magnon interactions in solid-state materials, and the ways in which these can be controlled.

AB - 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 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 is enhanced sevenfold 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 light on electron–magnon interactions in solid-state materials, and the ways in which these can be controlled.

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