Department of Physics, Hamburg University, Hamburg D-20355, Germany.
Institute for Molecules and Materials (IMM), Radboud University, Nijmegen 6525 AJ, The Netherlands.
Nat Nanotechnol. 2015 Nov;10(11):958-64. doi: 10.1038/nnano.2015.193. Epub 2015 Sep 7.
The recently proposed concept of a Hund's metal--a metal in which electron correlations are driven by Hund's rule coupling-can be used to explain the exotic magnetic and electronic behaviour of strongly correlated electron systems of multi-orbital metallic materials. Tuning the abundance of parameters that determine these materials is, however, experimentally challenging. Here, we show that the basic constituent of a Hund's metal--a Hund's impurity--can be realized using a single iron atom adsorbed on a platinum surface, a system that comprises a magnetic moment in the presence of strong charge fluctuations. The magnetic properties can be controlled by using the tip of a scanning tunnelling microscope to change the binding site and degree of hydrogenation of the 3d transition-metal atom. We are able to experimentally explore a regime of four almost degenerate energy scales (Zeeman energy, temperature, Kondo temperature and magnetic anisotropy) and probe the magnetic excitations with the microscope tip. The regime of our Hund's impurity can be tuned from an emergent magnetic moment to a multi-orbital Kondo state, and the system could be used to test predictions of advanced many-body theories for non-Fermi liquids in quantum magnets or unconventional superconductors.
最近提出的 Hund 金属概念——一种由 Hund 规则耦合驱动电子相关的金属——可用于解释多轨道金属材料强关联电子系统的奇异磁和电子行为。然而，调节决定这些材料的参数的丰度在实验上是具有挑战性的。在这里，我们表明 Hund 金属的基本组成部分——Hund 杂质——可以使用吸附在铂表面上的单个铁原子来实现，该系统在存在强电荷涨落的情况下具有磁矩。通过使用扫描隧道显微镜的尖端来改变 3d 过渡金属原子的结合位点和氢化程度，可以控制磁性。我们能够实验性地探索四个几乎简并的能量尺度（塞曼能、温度、Kondo 温度和磁各向异性）的范围，并使用显微镜尖端探测磁激发。我们 Hund 杂质的范围可以从出现的磁矩调谐到多轨道 Kondo 态，并且该系统可用于测试量子磁体中非费米液体或非常规超导体中先进的多体理论的预测。
