Invited Paper MI+2D+AC+NS-TuA7
Spin-orbit Coupled d-electron Surface States of Delafossite Oxides

Tuesday, October 31, 2017, 4:20 pm, Room 11

The ABO₂ family of delafossite oxide metals has recently found renewed prominence due to their remarkable transport properties. The Pd- and Pt-based cobaltates are the most conductive oxides known, with room-temperature resistivities lower per carrier even than copper metal [1,2]. Meanwhile, giant low-temperature mean-free paths of up to 10⁵ lattice spacings make hydrodynamic effects of the electron fluid observable in mesoscopic samples [3] and lead to a curious negative longitudinal magnetoresistance [4]. This is all underpinned by extremely broad bandwidths of the bulk electronic structure around the Fermi level, dominated by Pd/Pt-derived carriers that behave remarkably like free electrons [2], in part mediated by an unusual interplay with correlations which renders the Co block insulating. The crystal structure is polar, however, opening the potential for their surface electronic structures to be dramatically different to that of the bulk [5,6]. Here, we will show how these surfaces support strongly spin-split electronic states, and discuss the intriguing interplay of spin-orbit coupling and electronic interactions that they host.

Key collaborators on this work include Veronika Sunko (St Andrews and Max-Planck Institute for Chemical Physics of Solids, Dresden), Federico Mazzola (StA), and Helge Rosner, Pallavi Kushwaha, Seunghyum Khim, and Andy Mackenzie (MPI-CPFS).

[1] Hicks et al., Phys. Rev. Lett. 109 (2012) 116401

[2] Kushwaha et al., Science Adv. 1 (2015) e1500692

[3] Moll et al., Science 351 (2016) 6277

[4] Kikugawa et al., Nature Commun. 7 (2016) 10903

[5] Kim et al., Phys. Rev. B 80 (2009) 035116

[6] Noh et al., Phys. Rev. Lett. 102 (2009) 256404