Novel Electronic State and Superconductivity in the Electron-Doped High-Tc T'-Superconductors
Novel Electronic State and Superconductivity in the Electron-Doped High-Tc T'-Superconductors
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DOI：
10.3390/condmat2030023
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发表时间：
2017-07
期刊：
影响因子：
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通讯作者：
T. Adachi;T. Kawamata;Y. Koike
中科院分区：
文献类型：
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作者：
T. Adachi;T. Kawamata;Y. Koike
在这篇综述文章中，我们介绍了我们最近关于具有所谓的T‘结构的电子掺杂的高温铜酸盐中的非掺杂(无Ce)超导电性的研究结果。作为导言，我们简要地介绍了电子掺杂T‘-铜酸盐的特性，包括还原退火法、常规相图和非掺杂超导电性。然后，给出了我们的输运和磁学结果以及与未掺杂和欠掺杂T‘-CuPate的超导配对对称性有关的结果。还简要地给出了合作的光谱和核磁共振结果。研究发现，还原后的样品中载流子的强局域态伴随着反铁磁伪能隙，在还原的超导样品中转变为具有短程磁序的金属超导态。在还原的超导样品中由于极少量的过量氧而形成的短程磁序表明，在母化合物中表现出未掺杂超导电性的T‘-铜酸盐被认为是强关联的电子系统，以及空穴掺杂的高T_c铜酸盐。我们给出了我们提出的电子结构模型来理解非掺杂超导电性。最后，讨论了T‘-Cuprates尚未解决的未来问题。
In this review article, we show our recent results relating to the undoped (Ce-free) superconductivity in the electron-doped high- T c cuprates with the so-called T’ structure. For an introduction, we briefly mention the characteristics of the electron-doped T’-cuprates, including the reduction annealing, conventional phase diagram and undoped superconductivity. Then, our transport and magnetic results and results relating to the superconducting pairing symmetry of the undoped and underdoped T’-cuprates are shown. Collaborating spectroscopic and nuclear magnetic resonance results are also shown briefly. It has been found that, through the reduction annealing, a strongly localized state of carriers accompanied by an antiferromagnetic pseudogap in the as-grown samples changes to a metallic and superconducting state with a short-range magnetic order in the reduced superconducting samples. The formation of the short-range magnetic order due to a very small amount of excess oxygen in the reduced superconducting samples suggests that the T’-cuprates exhibiting the undoped superconductivity in the parent compounds are regarded as strongly correlated electron systems, as well as the hole-doped high- T c cuprates. We show our proposed electronic structure model to understand the undoped superconductivity. Finally, unsolved future issues of the T’-cuprates are discussed.