The polar surfaces of the delafossite oxides: from massive Rashba spin-splittings to itinerant surface ferromagnetism
DIPC Seminars
- Speaker
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Federico Mazzola, School of Physics and Astronomy, University of St. Andrews, Scotland, UK
- When
-
2020/03/09
13:00 - Place
- Donostia International Physics Center
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The ability to manipulate the surface and interface properties of correlated
electron systems underpins the burgeoning field of designer quantum matter.
Electronic reconstructions arising from polar interfaces have been widely
discussed as a way to drastically modify the interface electronic properties
of complex oxide heterostructures [1]. Here, we use angle-resolved
photoemission spectroscopy (ARPES) to show that an electronic reconstruction
occurs at the Pd-terminated polar surfaces of the delafossite oxides, PdCoO2
and PdCrO2. These compounds are wide-band metals in the bulk [2]. We
demonstrate how surface doping, as a result of their polarity-driven
electronic reconstruction, leads to a massive Rashba spin-splitting for the
CoO2 termination [3] and to a Stoner-instability towards itinerant
ferromagnetism for the Pd surface [4]. In particular, I will focus on the Pd
termination, where the polarity leads to a ferromagnetic surface atop a non-
magnetic bulk in PdCoO2, while in PdCrO2, which is a bulk antiferromagnet,
this forms a natural ferromagnetic-antiferromagnetic heterostructure. Our
ARPES measurements of the resulting multi-band electronic structures further
reveal spectroscopic signatures of a strong and highly tuneable coupling of
the surface electrons with magnon-modes. Our work thus paves the way for the
creation, control and manipulation of magnetic states at oxide surfaces and in
heterostructures, and shows how ARPES is a sensitive probe not only of their
surface magnetism, but also coupling with the collective magnetic excitations.
References
[1] Hwang et al., Nature Mater. 11, 103 (2012)
[2] MacKenzie, Rep. Prog. Phys. 80, 32501 (2017)
[3] Sunko V. et al., Nature 549, 492–496 (2017)
[4] Mazzola et al., PNAS, 115 (51) 12956-12960 (2018)
Host: Enrique Ortega