Université de Strasbourg , CNRS, IPCMS UMR 7504, F-67034 Strasbourg, France.
Karlsruher Institut für Technologie , Institut für Nanotechnologie, D-76344 Eggenstein-Leopoldshafen, Germany.
ACS Nano. 2017 Nov 28;11(11):10750-10760. doi: 10.1021/acsnano.7b05804. Epub 2017 Oct 6.
When single molecule magnets (SMMs) self-assemble into 2D networks on a surface, they interact via the π-electrons of their ligands. This interaction is relevant to the quantum entanglement between molecular qubits, a key issue in quantum computing. Here, we examine the role played by the unpaired radical electron in the top ligand of Tb double-decker SMMs by comparing the spectroscopic features of isolated and 2D assembled entities on surfaces. High-resolution scanning tunneling microscopy (STM) is used to evidence experimentally the Kondo resonance of the unpaired radical spins in clusters and islands and its quenching due to up-pairing at orbital overlaps. The presence or the absence of the Kondo feature in the dI/dV maps turns out to be a good measure of the lateral interaction between molecules in 2D networks. In a 2D cluster of molecules, the π-orbital lobes that are linked through the orbital overlap show paired-up electron wave function (one singly occupied molecular orbital (SOMO) with spin-up and the other with spin-down) and therefore do not experience the Kondo resonance in the experiment. As a result, small clusters built by STM-assisted manipulation of molecules show alternating Kondo features of quantum mechanical origin, from the monomer to the dimer and the trimer. On the other hand, when the TbPc molecular clusters grow larger and form extended domains, a geometric rearrangement occurs, leading to the quenching of the Kondo signal on one lobe out of two. The even distribution of overlapping (SOMO) lobes on the perimeter of the molecule is induced by the square symmetry of the semi-infinite lattice and clearly distinguishes the lattice from the clusters.
当单分子磁体 (SMM) 在表面自组装成 2D 网络时，它们通过配体的π电子相互作用。这种相互作用与分子量子位之间的量子纠缠有关，这是量子计算中的一个关键问题。在这里，我们通过比较表面上孤立和 2D 组装实体的光谱特征，研究了 Tb 双加层 SMM 顶部配体中未配对自由基电子的作用。高分辨率扫描隧道显微镜 (STM) 用于实验证据证明未配对自由基自旋在团簇和岛屿中的 Kondo 共振及其在轨道重叠时因配对而猝灭。在 dI/dV 图谱中 Kondo 特征的存在或不存在被证明是衡量 2D 网络中分子之间横向相互作用的良好指标。在分子的 2D 簇中，通过轨道重叠连接的π轨道叶瓣显示出配对的电子波函数（一个单占据分子轨道 (SOMO) 具有向上自旋，另一个具有向下自旋），因此在实验中不会经历 Kondo 共振。结果，通过 STM 辅助操纵分子构建的小团簇显示出交替的量子力学起源的 Kondo 特征，从单体到二聚体和三聚体。另一方面，当 TbPc 分子团簇生长得更大并形成扩展区域时，会发生几何重排，导致两个叶瓣中的一个叶瓣的 Kondo 信号猝灭。分子外围重叠（SOMO）叶瓣的均匀分布是由半无限晶格的正方形对称性引起的，这清楚地区分了晶格和团簇。
