Kushwaha Pallavi, Sunko Veronika, Moll Philip J W, Bawden Lewis, Riley Jonathon M, Nandi Nabhanila, Rosner Helge, Schmidt Marcus P, Arnold Frank, Hassinger Elena, Kim Timur K, Hoesch Moritz, Mackenzie Andrew P, King Phil D C
Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.
Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany. ; Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK.
Sci Adv. 2015 Oct 23;1(9):e1500692. doi: 10.1126/sciadv.1500692. eCollection 2015 Oct.
Understanding the role of electron correlations in strong spin-orbit transition-metal oxides is key to the realization 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 focused on the 5d iridium-based oxides. We instead consider the Pt-based delafossite oxide PtCoO2. Our transport measurements, performed on single-crystal samples etched to well-defined geometries using focused ion beam techniques, yield a room temperature resistivity of only 2.1 microhm·cm (μΩ-cm), 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 k z . Despite being predominantly composed of d-orbital character, the conduction band is remarkably steep, with an average effective mass of only 1.14m e. Moreover, the sharp spectral features observed in photoemission remain well defined with little additional broadening for more than 500 meV below E F, 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.
理解电子关联在强自旋轨道过渡金属氧化物中的作用是实现众多奇异相的关键，这些奇异相包括自旋轨道辅助的莫特绝缘体、关联拓扑固体以及潜在的新型高温超导体。迄今为止，大部分注意力都集中在基于5d铱的氧化物上。相反，我们考虑基于铂的铜铁矿氧化物PtCoO₂。我们对使用聚焦离子束技术蚀刻成明确几何形状的单晶样品进行的输运测量表明，其室温电阻率仅为2.1微欧·厘米（μΩ-cm），这使PtCoO₂成为已知导电性最强的氧化物。通过角分辨光电子能谱和密度泛函理论，我们表明其潜在的费米面是一个横截面近乎六边形的单圆柱，沿kz方向的色散非常弱。尽管导带主要由d轨道特征组成，但其非常陡峭，平均有效质量仅为1.14me。此外，在光电子能谱中观察到的尖锐光谱特征在低于费米能级（EF）超过500毫电子伏特的范围内仍保持清晰定义，几乎没有额外展宽，这表明电子 - 电子散射受到抑制。总之，我们的研究结果确立了PtCoO₂作为一种5d铜铁矿过渡金属氧化物中的近自由电子模型体系。
