近日，美国哥伦比亚大学Roy, Xavier团队揭示了二维晶格中轨道构型的受阻电子跃迁。这一研究成果于2025年8月7日发表在《自然—物理学》杂志上。
在空间周期晶格上的电子跳跃产生了有趣的电子行为。例如，跳跃在几何上从二维kagome、dice和Lieb晶格上产生的电子能带结构既具有无质量的狄拉克类能带，又具有完全无色散的扁平能带。由于具有骰子和里布晶格结构的材料很少，因此提出了一种利用原子轨道来实现几何衍射晶格特征电子跳变的替代方法。这一策略有望扩大具有辐照电子跳变的候选材料的名单，但尚未在实验中得到证实。
研究组证明了范德华金属间化合物Pd5AlI2的跃迁，它是由原子轨道排列在原始方形晶格中产生的。利用角分辨光发射光谱和量子振荡测量，研究组发现Pd5AlI2的能带结构包括线性狄拉克类能带，在它们的交叉点由局部平坦带相交-这是Lieb和dice晶格中散射跳变的基本特征。
此外，该化合物表现出优异的化学稳定性，其独特的体带结构和金属丰度在环境条件下一直保持到单层极限。因此，该结果展示了一种在非热化系统中实现几何热化晶格特征电子结构的方法。
附：英文原文
Title: Frustrated electron hopping from the orbital configuration in a two-dimensional lattice
Author: Devarakonda, Aravind, Koay, Christie S., Chica, Daniel G., Thinel, Morgan, Kundu, Asish K., Lin, Zhi, Georgescu, Alexandru B., Rossi, Sebastian, Han, Sae Young, Ziebel, Michael E., Holbrook, Madisen A., Rajapitamahuni, Anil, Vescovo, Elio, Watanabe, Kenji, Taniguchi, Takashi, Delor, Milan, Zhu, Xiaoyang, Pasupathy, Abhay N., Queiroz, Raquel, Dean, Cory R., Roy, Xavier
Issue&Volume: 2025-08-07
Abstract: Electron hopping on spatially periodic lattices gives rise to intriguing electronic behaviour. For example, hopping on the geometrically frustrated two-dimensional kagome, dice and Lieb lattices yields electronic band structures with both massless Dirac-like and perfectly dispersion-less, flat bands. As materials featuring the dice and Lieb lattice structures are scarce, an alternative approach proposes to leverage atomic orbitals to realize the characteristic electron hopping of geometrically frustrated lattices. This strategy promises to expand the list of candidate materials with frustrated electron hopping, but is yet to be shown in experiments. Here we demonstrate frustrated hopping in the van der Waals intermetallic Pd5AlI2, emerging from the arrangement of atomic orbitals in a primitive square lattice. Using angle-resolved photoemission spectroscopy and quantum oscillation measurements, we reveal that the band structure of Pd5AlI2 includes linear Dirac-like bands intersected at their crossing point by a locally flat band—an essential characteristic of frustrated hopping in Lieb and dice lattices. Moreover, this compound shows exceptional chemical stability, with its unusual bulk band structure and metallicity persisting in ambient conditions down to the monolayer limit. Hence, our results showcase a way to realize electronic structures characteristic of geometrically frustrated lattices in non-frustrated systems.
DOI: 10.1038/s41567-025-02953-2
Source: https://www.nature.com/articles/s41567-025-02953-2