发表机构
University of Illinois Chicago; The University of Texas at Austin; Argonne National Laboratory; Oak Ridge National Laboratory（伊利诺伊大学芝加哥分校; 德克萨斯大学奥斯汀分校; 阿贡国家实验室; 橡树岭国家实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
结合DFT、DMFT和cRPA，发现镥氢化物平带源于反位氢缺陷，关联强度由氢轨道占据主导，而非相互作用大小。
AI 中文摘要
镥氢化物（LuH$_x$，$1.75 \leq x \leq 3$）形成一系列多样的相，其中几种在压力下具有超导电性。由于氢缺陷形成的高倾向性，表征其电子性质一直具有挑战性，而最近的角分辨光电子能谱（ARPES）测量揭示了令人困惑的平带区域，这些区域使这些材料成为超导电性与平带物理可能交汇的候选材料。在此，通过结合密度泛函理论、动力学平均场理论和约束随机相位近似，我们揭示了这些平带的微观起源和关联性质。在所有组分中，由于氢轨道紧凑，H-s态的屏蔽库仑相互作用大于Lu-$d$态。然而，这些体系仍然是弱关联金属：几乎填满的H-$s$壳层允许很小的电荷涨落，因此其较大的相互作用表现为静态能级移动而非关联的来源。尽管在$x=2$时氢主要占据四面体位点，我们发现反位缺陷——即氢占据略微不利的八面体位点——同时产生ARPES平带特征和低能光学吸收峰，证实了这类材料在实验样品中通常具有缺陷性质。我们进一步发现，关联强度主要由这些位点上的氢轨道占据决定，而非相互作用大小本身。因此，我们确定氢轨道占据是决定镥氢化物中关联和低能平带物理的基本组织原则。
英文摘要
Lutetium hydrides (LuH$_x$, $1.75 \leq x \leq 3$) form a diverse series of phases, several of which superconduct under pressure. Characterizing their electronic properties has remained challenging owing to a high propensity for hydrogen defect formation, and recent angle-resolved photoemission (ARPES) measurements reveal puzzling flat-band regions that position these materials as candidates where superconductivity and flat-band physics may intersect. Here, by combining density functional theory, dynamical mean-field theory, and the constrained random-phase approximation, we uncover the microscopic origin and correlation nature of these flat bands. Across all compositions, the screened on-site Coulomb interaction is larger for H-s states than for Lu-$d$ states due to compact hydrogen orbitals. Nevertheless, these systems remain weakly correlated metals: the nearly filled H-$s$ shell admits little charge fluctuation, so its large interaction acts as a static level shift rather than a source of correlation. Although hydrogen primarily occupies tetrahedral sites at $x=2$, we discover that anti-site defects--where hydrogens occupy slightly unfavorable octahedral sites--generate both the ARPES flat-band features and the low-energy optical absorption peak, attesting to the usual defective nature of such materials in experimental samples. We further find that correlation strength is governed primarily by hydrogen orbital filling at these sites rather than the interaction magnitude itself. Consequently, we identify hydrogen orbital filling as the fundamental organizing principle dictating correlation and low-energy flat-band physics in lutetium hydrides.
Comments12 pages, 6 figures
