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arXiv 2102.02034cond-mat.str-el
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立方相Pu₃Ga中的准粒子多重态塌缩与5f巡游-局域交叉

Collapse of quasiparticle multiplets and $5f$ itinerant-localized crossovers in cubic phase Pu$_{3}$Ga

Li Huang, Haiyan Lu

AI总结:

本研究结合密度泛函理论与嵌入动力学平均场理论,发现立方相Pu₃Ga存在轨道选择型5f巡游-局域交叉及温度驱动的电子利夫希茨转变,为理解钚-镓体系的相稳定机制提供了电子结构层面的依据。

摘要:

钚及钚基金属间化合物的物理性质对温度、压强和化学合金化极为敏感。一个著名的例子是高温δ相钚,可通过掺杂少量三价金属杂质(如镓或铝)使其在室温下稳定存在。立方相Pu₃Ga是钚-镓金属间化合物之一,对理解钚-镓体系的相稳定性和相变具有关键作用,其电子结构可能是揭示δ相钚-镓合金稳定机制的核心。本工作结合密度泛函理论和嵌入动力学平均场理论,研究了立方相Pu₃Ga随温度变化的关联电子态。我们识别出可随温度发生的轨道选择型5f巡游-局域(相干-非相干)交叉。实际上存在两个差异显著的电子相干温度:较高的对应5f_{5/2}态[T_{coh}(5f_{5/2})≈700 K],较低的对应5f_{7/2}态[T_{coh}(5f_{7/2})≈100 K]。此外,源于5f⁴、5f⁵和5f⁶电子构型间多体跃迁的准粒子多重态会逐渐衰减,局域5f能带与导带之间的杂化被高温抑制,进而导致费米面拓扑结构改变,这标志着温度驱动的电子Lifshitz(利夫希茨)转变。最后,计算得到T=80 K时的线性比热系数γ约为112 mJ/(mol K²)。

英文摘要:

The physical properties of plutonium and plutonium-based intermetallic compounds are extremely sensitive to temperature, pressure, and chemical alloying. A celebrated example is the high-temperature $δ$ phase plutonium, which can be stabilized at room temperature by doping it with a few percent trivalent metal impurities, such as gallium or aluminum. The cubic phase Pu$_{3}$Ga, one of the plutonium-gallium intermetallic compounds, plays a key role in understanding the phase stability and phase transformation of the plutonium-gallium system. Its electronic structure might be essential to figure out the underlying mechanism that stabilizes the $δ$ phase plutonium-gallium alloy. In the present work, we studied the temperature-dependent correlated electronic states of cubic phase Pu$_{3}$Ga by means of a combination of the density functional theory and the embedded dynamical mean-field theory. We identified orbital selective 5$f$ itinerant-localized (coherent-incoherent) crossovers which could occur upon temperature. Actually, there exist two well-separated electronic coherent temperatures. The higher one is for the $5f_{5/2}$ state [$T_{\text{coh}}(5f_{5/2}) \approx 700$ K], while the lower one is for the $5f_{7/2}$ state [$T_{\text{coh}}(5f_{7/2}) \approx 100$ K]. In addition, the quasiparticle multiples which originate from the many-body transitions among the $5f^{4}$, $5f^{5}$, and $5f^{6}$ electronic configurations, decay gradually. The hybridizations between the localized 5$f$ bands and conduction bands are subdued by high temperature. Consequently, the Fermi surface topology is changed, which signals a temperature-driven electronic Lifshitz transition. Finally, the calculated linear specific heat coefficient $γ$ is approximately 112 mJ / (mol K$^2$) at $T = 80$ K.

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