结构复杂的$\sigma$相Re-X（X = V, Nb, Ta）合金及其衍生中熵合金中的超导电性
Superconductivity in structurally complex $σ$-Phase Re-X (X = V, Nb, Ta) and a derived medium-entropy alloys
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中文总结 AI 辅助
本研究合成了$\sigma$相Re-X（X=V, Nb, Ta）合金及衍生中熵合金，通过磁化、电阻和比热测量证实其体相II型超导性，电子比热符合弱耦合BCS行为，为研究结构复杂性与化学无序对超导的影响提供了模型体系。
中文摘要 AI 辅助
结构复杂的四方$\sigma$相为研究化学无序、电子结构与超导电性之间的相互作用提供了一个独特的平台，特别是在Re基合金中，非常规超导电性已被广泛讨论。本文中，我们合成了$\sigma$相Re-X（X = V, Nb, Ta）合金，其成分为Re$_{0.76}$V$_{0.24}$、Re$_{0.56}$Nb$_{0.44}$和Re$_{0.60}$Ta$_{0.40}$，并研究了它们的超导性质。这些成分位于$\sigma$相的狭窄稳定范围内，突显了价电子浓度在相形成中的关键作用。为了考察增强化学无序的影响，我们进一步合成了由这些二元体系衍生的结构复杂中熵合金Re$_{0.56}$Nb$_{0.19}$Ta$_{0.19}$V$_{0.06}$。磁化率、电阻率和比热测量确立了所有化合物中体相II型超导电性的存在。电子比热分析结果与完全能隙、弱耦合BCS超导态一致。相反，正常态电阻率表现出非常规的负温度系数，且由电阻率测量得到的超导转变温度值高于其他测量所得值。我们的结果表明，$\sigma$相Re-X合金（涵盖3d、4d和5d过渡金属替代）及其对应中熵合金构成了一个具有吸引力的模型体系家族，可用于研究结构复杂性、化学无序和自旋-轨道耦合对Re基材料超导电性的影响。
英文摘要
The structurally complex tetragonal sigma ($σ$)-phase provides a unique platform for investigating the interplay between chemical disorder, electronic structure, and superconductivity, particularly in Re-based alloys where unconventional superconductivity has been widely discussed. Here, we synthesize and investigate the superconducting properties of $σ$-phase Re-X (X = V, Nb, and Ta) alloys with compositions Re$_{0.76}$V$_{0.24}$, Re$_{0.56}$Nb$_{0.44}$, and Re$_{0.60}$Ta$_{0.40}$. These compositions lie within the narrow stability range of the $σ$ phase, underscoring the critical role of valence electron concentration in phase formation. To examine the influence of enhanced chemical disorder, we further synthesize the structurally complex medium-entropy alloy Re$_{0.56}$Nb$_{0.19}$Ta$_{0.19}$V$_{0.06}$, derived from these binary systems. Magnetization, electrical resistivity, and specific-heat measurements establish bulk type-II superconductivity in all compounds. Analysis of the electronic heat capacity is consistent with a fully gapped, weak-coupling BCS superconducting state. In contrast, the normal-state resistivity exhibits an unconventional negative temperature coefficient, and the superconducting transition temperature values obtained from resistivity measurements are higher than those determined from other measurements. Our results demonstrate that both the $σ$-phase Re-X alloys, spanning 3d, 4d, and 5d transition-metal substitutions, and their medium-entropy counterpart constitute an attractive family of model systems for investigating the effects of structural complexity, chemical disorder, and spin-orbit coupling on superconductivity in Re-based materials.
发表机构
- Gdansk University of Technology（格但斯克理工大学）
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