The recently discovered nickelate superconductors appear, at first glance, to be even more complicated multi-orbital systems than cuprates. To identify the simplest model describing the nickelates, we analyse the multi-orbital system and find that it is instead the nickelates which can be described by a one-band Hubbard model, albeit with an additional electron reservoir and only around the superconducting regime. Our calculations of the critical temperature T_C are in good agreement with experiment, and show that optimal doping is slightly below 20% Sr-doping. Even more promising than 3d nickelates are 4d palladates.

中文翻译：

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镍超导体-单波段Hubbard模型的复兴

乍一看，最近发现的镍酸盐超导体似乎比铜酸盐更复杂的多轨道系统。为了识别描述镍酸盐的最简单模型，我们分析了多轨道系统，发现可以用单波段Hubbard模型描述的是镍酸盐，尽管它带有附加的电子储集层并且仅在超导范围内。我们对临界温度T _C的计算与实验吻合良好，表明最佳掺杂略低于20％Sr掺杂。比3d镍酸盐更有前景的是4d钯酸盐。