近日，美国麻省理工学院Riccardo Comin团队报道了在氧化尖晶石中发现了亨德扁平带。这一研究成果于2025年11月6日发表在《美国科学院院刊》杂志上。
与淬火动能和重电子质量相关的电子平带在促进强电子相关和高温电荷分馏和超导等紧急现象方面引起了人们的极大兴趣。大量的实验和理论研究一直致力于建立与这种局域电子态交织在一起的丰富的非平凡金属和重费米子相。
研究组分析了过渡金属氧化物尖晶石LiV2O4，这是一种缺乏局域轨道态的神秘重费米子化合物。研究组利用角分辨光发射光谱和动力学平均场理论揭示了一种由原子内亨德耦合引起的抑制原子间电子跳变的相关诱导平带。重准粒子的出现被归因于一个近似的轨道选择性莫特态，其特征是局域矩的波动，这是由互补磁输运测量所证明的。
长寿命准粒子的光谱指纹及其随温度升高而消失，进一步支持了输运数据中观察到的高温“坏”金属态的出现。这项工作解决了一个长期存在的难题，即重费米子行为的起源和LiV2O4中的非常规输运。同时，它开辟了一条途径，通过电子相互作用，在d轨道系统与几何热化实现平坦带，有可能实现奇异相的物质，如分馏费米液体。
附：英文原文
Title: Hund’s flat band in a frustrated spinel oxide
Author: Oh, Dongjin, Hampel, Alexander, Wakefield, Joshua P., Moen, Peter C., Smit, Steef, Luo, Xiangyu, Zonno, Marta, Gorovikov, Sergey, Leandersson, Mats, Polley, Craig, Kundu, Asish K., Rajapitamahuni, Anil, Vescovo, Elio, Jozwiak, Chris, Bostwick, Aaron, Rotenberg, Eli, Isobe, Masahiko, Verma, Manish, Crispino, Matteo, Grundner, Martin, Kugler, Fabian B., Parcollet, Olivier, Schollwck, Ulrich, Takagi, Hidenori, Damascelli, Andrea, Sangiovanni, Giorgio, Checkelsky, Joseph G., Georges, Antoine, Comin, Riccardo
Issue&Volume: 2025-11-6
Abstract: Electronic flat bands associated with quenched kinetic energy and heavy electron mass have attracted great interest for promoting strong electronic correlations and emergent phenomena such as high-temperature charge fractionalization and superconductivity. Intense experimental and theoretical research has been devoted to establishing the rich nontrivial metallic and heavy fermion phases intertwined with such localized electronic states. Here, we investigate the transition metal oxide spinel LiV2O4, an enigmatic heavy fermion compound lacking localized f orbital states. We use angle-resolved photoemission spectroscopy and dynamical mean-field theory to reveal a kind of correlation-induced flat band with suppressed interatomic electron hopping arising from intra-atomic Hund’s coupling. The appearance of heavy quasiparticles is ascribed to a proximate orbital-selective Mott state characterized by fluctuating local moments as evidenced by complementary magnetotransport measurements. The spectroscopic fingerprints of long-lived quasiparticles and their disappearance with increasing temperature further support the emergence of a high-temperature “bad” metal state observed in transport data. This work resolves a long-standing puzzle on the origin of heavy fermion behavior and unconventional transport in LiV2O4. Simultaneously, it opens a path to achieving flat bands through electronic interactions in d-orbital systems with geometrical frustration, potentially enabling the realization of exotic phases of matter such as the fractionalized Fermi liquids.
DOI: 10.1073/pnas.2518213122
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2518213122