近日，美国哥伦比亚大学Pasupathy, Abhay N.团队研究了二维重费米子材料中的节点杂化。该项研究成果发表在2025年10月14日出版的《自然—物理学》杂志上。
具有部分填充核心原子壳层的金属，由于核心能级和传导电子的杂化，可以在低温下形成准粒子。这些金属的热力学和光谱性质可以理解为简单金属的性质，但具有比自由电子质量（通常称为重费米子）显著的质量增强。在大多数重费米子材料中，杂化在位置和动量空间上近似各向同性。然而，核能级波函数的低维性和对称性的结合可以引起与传导电子的高度各向异性电子相互作用。
研究组证明了在基于镧系元素的二维范德华重费米子化合物CeSiI中，沿动量空间（称为节点）的特定方向消失的各向异性杂化。准粒子干涉测量揭示了费米表面上一组具有高光谱强度的离散热点。理论建模和与非重费米子等结构类似物LaSiI的准粒子干涉模式的比较表明，这些特征是由CeSiI特有的涉及杂交节点的非常规电子相互作用引起的。结果，准粒子的有效质量根据它们在动量空间中的方向以数量级变化。
附：英文原文
Title: Nodal hybridization in a two-dimensional heavy-fermion material
Author: Turkel, Simon, Posey, Victoria A., Ong, Chin Shen, Ghosh, Sanat, Huang, Xiong, Kundu, Asish K., Vescovo, Elio, Chica, Daniel G., Thunstrm, Patrik, Eriksson, Olle, Simeth, Wolfgang, Scheie, Allen, Rubio, Angel, Millis, Andrew J., Roy, Xavier, Pasupathy, Abhay N.
Issue&Volume: 2025-10-14
Abstract: Metals with partially filled core atomic shells can form quasiparticles at a low temperature arising from the hybridization of the core level and conduction electrons. The thermodynamic and spectroscopic properties of these metals can be understood as those of a simple metal, but with a significant mass enhancement over the free electron mass—commonly referred to as heavy fermions. In most heavy-fermion materials, the hybridization is approximately isotropic in position and momentum space. However, a combination of low dimensionality and symmetry properties of the core-level wavefunctions can give rise to highly anisotropic electronic interactions with the conduction electrons. Here we demonstrate anisotropic hybridization that vanishes along specific directions in momentum space—referred to as nodes—in a lanthanide-based two-dimensional van der Waals heavy-fermion compound, CeSiI. Quasiparticle interference measurements reveal a set of discrete hotspots with high spectral intensity on the Fermi surface. Theoretical modelling and comparison with the quasiparticle interference pattern of the non-heavy-fermion isostructural analogue LaSiI suggest that these features arise from an unconventional electron interaction involving hybridization nodes unique to CeSiI. As a result, the effective mass of the quasiparticles varies by orders of magnitude depending on their direction in momentum space.
DOI: 10.1038/s41567-025-03060-y
Source: https://www.nature.com/articles/s41567-025-03060-y