The delafossite metals PdCoO${}_2$, PtCoO${}_2$ and PdCrO${}_2$ are among the highest conductivity materials known, with low temperature mean free paths of tens of microns in the best as-grown single crystals. A key question is whether these very low resistive scattering rates result from strongly suppressed backscattering due to special features of the electronic structure, or are a consequence of highly unusual levels of crystalline perfection. We report the results of experiments in which high energy electron irradiation was used to introduce point disorder to the Pd and Pt layers in which the conduction occurs. We obtain the cross-section for formation of Frenkel pairs in absolute units, and cross-check our analysis with first principles calculations of the relevant atomic displacement energies. We observe an increase of resistivity that is linear in defect density with a slope consistent with scattering in the unitary limit. Our results enable us to deduce that the as-grown crystals contain extremely low levels of in-plane defects of approximately $0.001\%$. This confirms that crystalline perfection is the most important factor in realizing the long mean free paths, and highlights how unusual these delafossite metals are in comparison with the vast majority of other multi-component oxides and alloys. We discuss the implications of our findings for future materials research.

中文翻译：

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通过电子辐照控制将缺陷引入铝铁矿金属

铜铁矿金属PdCoO${}_2$铂${}_2$ 和PdCrO${}_2$在已知的最高电导率材料中，最好的成年单晶具有平均数十微米的低温平均自由程。一个关键的问题是，这些非常低的电阻散射率是由于电子结构的特殊功能而强烈抑制了反向散射，还是由于极高水平的晶体完美化所致。我们报告了使用高能电子辐射将点无序引入发生导电的Pd和Pt层的实验结果。我们获得了以绝对单位形成弗伦克尔对的横截面，并通过相关原子位移能的第一性原理计算对我们的分析进行了核对。我们观察到电阻率在缺陷密度中呈线性增长，其斜率与单位极限中的散射一致。我们的结果使我们可以推断出，所生长的晶体包含极低水平的面内缺陷，约为$0.001％$。这证实了晶体的完美是实现长的平均自由程的最重要因素，并突显了与大多数其他多组分氧化物和合金相比，这些非铁矿金属是多么不寻常。我们讨论了我们的发现对未来材料研究的意义。