Temperature-Independent Cuprate Pseudogap from Planar Oxygen NMR
Temperature-Independent Cuprate Pseudogap from Planar Oxygen NMR
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DOI：
10.3390/condmat5040066
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发表时间：
2020-12-01
期刊：
影响因子：
1.7
通讯作者：
Haase, Jurgen
中科院分区：
文献类型：
--
作者：
Nachtigal, Jakob;Avramovska, Marija;Haase, Jurgen
平面氧核磁共振（NMR）弛豫和位移数据从所有铜超导体在文献中可用的分析。它们揭示了费米表面存在一个与温度无关的赝隙，该赝隙以特定于家族的方式随着掺杂的减少而增加，即对于某些材料，在最佳掺杂时赝隙很大，而对于其他材料，在最佳掺杂时赝隙几乎关闭。赝隙以上或无赝隙的状态在所有铜酸盐和掺杂水平下都是相似的，并且是类似费米液体的。如果假设赝隙是指数型的，对于大多数欠掺杂体系，赝隙可以大到约1500k，这与交换耦合有关。赝隙可以在整个材料中变化很大，是铜在电荷和自旋方面不均匀性的原因，因此讨论了核磁共振分析的后果。这种赝隙似乎与很久以前测量的YBaCuO系列材料的比热数据一致。在T-c附近，核弛豫和位移显示出与这种情况的偏差，可能是由于其他间隙态。
Planar oxygen nuclear magnetic resonance (NMR) relaxation and shift data from all cuprate superconductors available in the literature are analyzed. They reveal a temperature-independent pseudogap at the Fermi surface, which increases with decreasing doping in family-specific ways, i.e., for some materials, the pseudogap is substantial at optimal doping while for others it is nearly closed at optimal doping. The states above the pseudogap, or in its absence are similar for all cuprates and doping levels, and Fermi liquid-like. If the pseudogap is assumed exponential it can be as large as about 1500 K for the most underdoped systems, relating it to the exchange coupling. The pseudogap can vary substantially throughout a material, being the cause of cuprate inhomogeneity in terms of charge and spin, so consequences for the NMR analyses are discussed. This pseudogap appears to be in agreement with the specific heat data measured for the YBaCuO family of materials, long ago. Nuclear relaxation and shift show deviations from this scenario near T-c, possibly due to other in-gap states.