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arXiv 2201.11189cond-mat.str-el
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UGe2中共存的近藤杂化和巡游f电子铁磁性

Coexisting Kondo hybridization and itinerant f-electron ferromagnetism in UGe2

Ioannis Giannakis, Divyanshi Sar, Joel Friedman, Chang-Jong Kang, Marc Janoschek, Pinaki Das, Eric D. Bauer, Gabriel Kotliar, Pegor Aynajian

摘要:

近藤杂化在部分填充的f-电子系统中传递了大量的电子态,这些电子态急剧接近费米能,导致从超导到奇异电子序的各种不稳定性。UGe 2是一个5 f重费米子系统,在Tc ~ 52 K的二级跃迁和Tx ~ 32 K的交叉跃迁下,Kondo杂化被两个铁磁相的形成所打断。这两个铁磁相伴随着自旋三重态超导性,只出现在高压下的磁有序相内并持续存在。这两个铁磁相的起源以及它们如何在近藤晶格中形成仍然不清楚。使用扫描隧道显微镜和光谱,我们探测的空间电子状态的UGe 2作为温度的函数。根据我们的密度泛函理论(DFT)+ Gutzwiller计算,我们发现了一个近藤共振和尖锐的5 f电子态附近的化学势,在高温下形成Tc以上。当温度降低到Tc以下时,共振变窄,并最终在费米能量处分裂到Tx以下,从而倾倒巡回f电子光谱权重。我们的研究结果表明,在Tx以下形成高度极化铁磁相的Stoner机制本身为高压下非常规超导性的出现奠定了基础。

英文摘要:

Kondo hybridization in partially filled f-electron systems conveys significant amount of electronic states sharply near the Fermi energy leading to various instabilities from superconductivity to exotic electronic orders. UGe2 is a 5f heavy fermion system, where the Kondo hybridization is interrupted by the formation of two ferromagnetic phases below a 2nd order transition Tc ~ 52 K and a crossover transition Tx ~ 32 K. These two ferromagnetic phases are concomitantly related to a spin-triplet superconductivity that only emerges and persists inside the magnetically ordered phase at high pressure. The origin of the two ferromagnetic phases and how they form within a Kondo-lattice remain ambiguous. Using scanning tunneling microscopy and spectroscopy, we probe the spatial electronic states in the UGe2 as a function of temperature. We find a Kondo resonance and sharp 5f-electron states near the chemical potential that form at high temperatures above Tc in accordance with our density functional theory (DFT) + Gutzwiller calculations. As temperature is lowered below Tc, the resonance narrows and eventually splits below Tx dumping itinerant f-electron spectral weight right at the Fermi energy. Our findings suggest a Stoner mechanism forming the highly polarized ferromagnetic phase below Tx that itself sets the stage for the emergence of unconventional superconductivity at high pressure.

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