Nearly free electrons in a 5d delafossite oxide metal.
Nearly free electrons in a 5d delafossite oxide metal.
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DOI：
10.1126/sciadv.1500692
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发表时间：
2015-10
期刊：
影响因子：
13.6
通讯作者：
King PD
中科院分区：
文献类型：
--
作者：
Kushwaha P;Sunko V;Moll PJ;Bawden L;Riley JM;Nandi N;Rosner H;Schmidt MP;Arnold F;Hassinger E;Kim TK;Hoesch M;Mackenzie AP;King PD
运输和ARPES显示非常好的金属性所产生的几乎自由电子的行为在单晶PtCoO 2。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许多奇异相的关键，包括自旋轨道辅助莫特绝缘体，相关拓扑固体和未来的新高温超导体。迄今为止，大多数注意力都集中在5d铱基氧化物上。相反，我们考虑基于Pt的铜铁矿氧化物PtCoO 2。我们的传输测量，使用聚焦离子束技术蚀刻到明确的几何形状的单晶样品上进行，产生的室温电阻率仅为2.1 microhm·cm（μΩ-cm），建立PtCoO 2作为已知的最导电的氧化物。从角分辨光电子能谱和密度泛函理论，我们表明，下面的费米面是一个单一的圆柱体的近六边形横截面，具有非常弱的色散沿着kz。尽管导带主要由d轨道组成，但导带非常陡峭，平均有效质量仅为1.14me。此外，在光电子发射中观察到的尖锐的光谱特征仍然很好地定义，几乎没有额外的扩大超过500毫电子伏以下EF，指向抑制电子-电子散射。总之，我们的研究结果建立PtCoO 2作为一个模型的近自由电子系统在5D铜铁矿过渡金属氧化物。
Transport and ARPES reveal extremely good metallicity arising from almost free-electron behavior in single-crystal PtCoO2. 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 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 more than 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.