Understanding the role of electron correlations in strong spin-orbit transition-metal oxides is key to the realisation of numerous exotic phases including spin-orbit assisted Mott insulators, correlated topological solids, and prospective new high-temperature superconductors. To date, most attention has been focussed on the 5d iridium-based oxides. Here, we instead consider the Pt-based delafossite oxide PtCoO2. Our transport measurements, performed on single-crystal samples etched to well-defined geometries using focussed ion-beam techniques, yield a room-temperature resistivity of only 2.1~μΩcm, establishing PtCoO2 as the most conductive oxide known. From angle-resolved photoemission and density-functional theory, we show that the underlying Fermi surface is a single cylinder of nearly hexagonal cross-section, with very weak dispersion along kz. Despite being predominantly composed of d-orbital character, the conduction band is remarkably steep, with an average effective mass of only 1.14me. Moreover, the sharp spectral features observed in photoemission remain well-defined with little additional broadening for over 500~meV below EF, pointing to suppressed electron-electron scattering. Together, our findings establish PtCoO2 as a model nearly-free electron system in a 5d delafossite transition-metal oxide.
@article{arxiv.1510.02439,
title = {Nearly-free electrons in a 5d delafossite oxide metal},
author = {Pallavi Kushwaha and Veronika Sunko and P. J. W. Moll and L. Bawden and J. M. Riley and Nabhanila Nandi and H. Rosner and M. P. Schmidt and F. Arnold and E. Hassinger and T. K. Kim and M. Hoesch and A. P. Mackenzie and P. D. C. King},
journal= {arXiv preprint arXiv:1510.02439},
year = {2015}
}
Comments
Accepted in Science Advances. arXiv admin note: text overlap with arXiv:1411.6162