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arXiv 2008.07573cond-mat.supr-con
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铜酸盐高温超导体La1. 6-xNd0. 4SrxCuO 4的材料制备、单晶生长及phase diagram

Materials preparation, single crystal growth, and the phase diagram of the cuprate high temperature superconductor La1.6-xNd0.4SrxCuO4

Mirela Dragomir, Qianli Ma, J. Patrick Clancy, Amirreza Ataei, Paul A. Dube, Sudarshan Sharma, Ashfia Huq, Hanna A. Dabkowska, Louis Taillefer, Bruce D. Gaulin

摘要:

La-214系列铜酸盐超导体的一个分支,La 1.6-xNd 0.4SrxCuO 4(Nd-LSCO),已经引起了显著和持续的兴趣,在很大程度上是因为它显示了典型空穴掺杂的高Tc超导性的相图的全部复杂性,同时还显示出相对低的超导临界温度。低的超导Tc意味着实验上可获得的磁场可以将超导性抑制到零温度。特别是,这使得各种运输和热力学研究的T = 0基态在Nd-LSCO,超导电性,跨越临界掺杂p *= 0.23的赝能隙相结束。它的超导性质对它的晶体对称性的强烈依赖本身就激发了对Nd-LSCO结构相图的仔细研究。本文对Nd-LSCO单晶和多晶样品的材料制备和表征进行了系统的研究和总结。单相多晶样品与x跨越范围从0.01到0.40已合成,和大单晶的Nd-LSCO选择x跨越该区域(0.07,0.12,0.17,0.19,0.225,0.24,和0.26)生长的光学浮区法。系统的中子和X射线衍射研究,这些样品进行了在低温和室温下,10 K和300 K,分别。这些研究使我们能够跟踪各种结构相变,并提出了一个更新的结构相图Nd-LSCO。特别地,我们发现低温四氢呋喃(LTT)相在临界掺杂pLTT = 0.255(5)处结束,与p * 清楚地分离。

英文摘要:

One branch of the La-214 family of cuprate superconductors, La1.6-xNd0.4SrxCuO4 (Nd-LSCO), has been of significant and sustained interest, in large part because it displays the full complexity of the phase diagram for canonical hole-doped, high Tc superconductivity, while also displaying relatively low superconducting critical temperatures. The low superconducting Tc's imply that experimentally accessible magnetic fields can suppress the superconductivity to zero temperature. In particular, this has enabled various transport and thermodynamic studies of the T = 0 ground state in Nd-LSCO, free of superconductivity, across the critical doping p* = 0.23 where the pseudogap phase ends. The strong dependence of its superconducting properties on its crystal symmetry has itself motivated careful studies of the Nd-LSCO structural phase diagram. This paper provides a systematic study and summary of the materials preparation and characterization of both single crystal and polycrystalline samples of Nd-LSCO. Single-phase polycrystalline samples with x spanning the range from 0.01 to 0.40 have been synthesized, and large single crystals of Nd-LSCO for select x across the region (0.07, 0.12, 0.17, 0.19, 0.225, 0.24, and 0.26) were grown by the optical floating zone method. Systematic neutron and X-ray diffraction studies on these samples were performed at both low and room temperatures, 10 K and 300 K, respectively. These studies allowed us to follow the various structural phase transitions and propose an updated structural phase diagram for Nd-LSCO. In particular, we found that the low-temperature tetragonal (LTT) phase ends at a critical doping pLTT = 0.255(5), clearly separated from p*.

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