Minati F, Tomassucci G, Hattori M, Fujita Y, Nagao M, Tortora L, Barinov A, Kopciuszynski M, Campi G, Boeri L, Mizokawa T, Saini N L
Dipartimento di Fisica, Università di Roma "La Sapienza", P. Aldo Moro 2, 00185 Roma, Italy.
Department of Applied Physics, Waseda University, Shinjuku, 169-8555 Tokyo, Japan.
Inorg Chem. 2025 Jun 9;64(22):11260-11267. doi: 10.1021/acs.inorgchem.5c01680. Epub 2025 May 29.
Two decades after the discovery of high-entropy alloys (HEAs), the field has witnessed these systems rise as prominent examples of high-performance functional materials, overcoming established knowledge of multicomponent systems. HEA superconductors are currently under thorough investigation due to their robust superconducting state and the possibility of enhancing their figure of merit through the high-entropy approach, in addition to the well-known mechanical and thermal properties of these materials. Here, we have investigated the electronic structure of HEA-type REOBiS layered superconductors (RE = rare earth) using spectromicroscopy and angle-resolved photoemission spectroscopy (ARPES) with a submicron beam size. The overall features of the fundamental electronic structure are robust, showing limited effects of mixing entropy. We find an inherent coexistence of phases driven by local fluctuations in the interlayer interactions. This coexistence exhibits distinct patterns for different samples characterized by varying configurational entropy. Similarly, the Luttinger volume estimated from the ARPES spectra reveals differing self-doping regimes, indicating that RE valence fluctuations are possibly influenced by configurational disorder. Overall, this study represents the first report on the electronic structure of HEA-type BiS-based superconductors and provides valuable insight into controlling superconducting properties by tailoring nano- to microstructures through a high-entropy approach.
在发现高熵合金（HEAs）二十年后，该领域见证了这些体系作为高性能功能材料的突出范例而兴起，突破了多组分体系的既有认知。HEA 超导体目前正受到深入研究，这是因为它们具有稳健的超导态，除了这些材料众所周知的机械和热性能外，还可通过高熵方法提高其品质因数。在此，我们使用亚微米束尺寸的光谱显微镜和角分辨光电子能谱（ARPES）研究了 HEA 型 REOBiS 层状超导体（RE = 稀土）的电子结构。基本电子结构的整体特征较为稳健，显示出混合熵的影响有限。我们发现由层间相互作用的局部涨落驱动的相的固有共存。这种共存对于以不同构型熵为特征的不同样品呈现出不同的模式。同样，从 ARPES 光谱估计的卢廷格体积揭示了不同的自掺杂机制，表明 RE 价态涨落可能受构型无序的影响。总体而言，本研究是关于 HEA 型 BiS基超导体电子结构的首份报告，并通过高熵方法定制纳米至微观结构，为控制超导性能提供了有价值的见解。
