Li Donglin, Cao Nan, Metzelaars Marvin, Silveira Orlando J, Jestilä Joakim, Fumega Adolfo, Nishiuchi Tomohiko, Lado Jose, Foster Adam S, Kubo Takashi, Kawai Shigeki
Center for Basic Research on Materials, National Institute for Materials Science, 1-2-1 Segen, Tsukuba, Ibaraki 305-0047, Japan.
Department of Applied Physics, Aalto University, Espoo 02150, Finland.
J Am Chem Soc. 2025 Jul 30;147(30):26208-26217. doi: 10.1021/jacs.5c03112. Epub 2025 Jul 11.
Frustrated spin systems, where competing interactions prevent conventional magnetic ordering, provide a platform for uncovering emergent quantum phases and exotic many-body phenomena. Particularly, low-dimensional and symmetric geometries without boundary conditions allow us to study unconventional spin states. Here, we present = 1/2 antiferromagnetic Heisenberg cyclic pentamer and hexamer via homocoupling of air-stable phenalenyl derivatives on Au(111). With a combination of scanning tunneling microscopy (STM)/scanning tunneling spectroscopy (STS) at 4.3 K and comprehensive theoretical simulations, we found that while large magnetic exchange interactions exist in both rings, the pentamer features an increased geometric frustration of the system. This frustration induces rotational symmetry in the spin wave function, leading to a 4-fold degenerate ground states of the pentamer. The interplay between molecular geometry and magnetic interactions creates a unique quantum spin environment. Our findings offer a powerful approach for constructing spin-frustrated molecular architectures, allowing precise control over quantum magnetic interactions.
受挫自旋系统中，相互竞争的相互作用阻碍了传统的磁有序，为揭示新兴量子相和奇异多体现象提供了一个平台。特别是，没有边界条件的低维和对称几何结构使我们能够研究非常规自旋态。在这里，我们通过在Au(111)上对空气稳定的苊烯基衍生物进行同偶联，展示了S = 1/2反铁磁海森堡环状五聚体和六聚体。结合4.3 K下的扫描隧道显微镜(STM)/扫描隧道谱(STS)以及全面的理论模拟，我们发现虽然两个环中都存在大的磁交换相互作用，但五聚体的系统几何受挫增加。这种受挫在自旋波函数中诱导了旋转对称性，导致五聚体的基态出现四重简并。分子几何结构与磁相互作用之间的相互作用创造了独特的量子自旋环境。我们的发现为构建自旋受挫分子结构提供了一种有力方法，能够精确控制量子磁相互作用。
