Magnetic excitations of single atoms and molecules on superconductors probed by scanning tunneling spectroscoppy

在这个方案的框架下，我们将在原子尺度上解决原子和分子自旋与超导衬底的基本相互作用机制。吸附的磁矩通过交换作用耦合到衬底的传导电子和库珀对上。一方面，这导致通过所谓的近藤效应屏蔽磁矩，另一方面，库珀对的配对能量发生变化，这反映在超导能隙内的Shiba态中。这些过程的竞争产生了一个复杂的多体状态，我们将使用扫描隧道光谱来解决这个问题。在之前的工作中，我们可以实验证明近藤屏蔽的效率与自旋1/2系统中Shiba态的能量之间的普遍关联，这是几十年前理论预测的结果。有了这些结果，原子环境的微小差异也变得很明显，对由此产生的磁基态产生了至关重要的影响。我们现在将增加自旋系统及其环境的复杂性，以便将更多因素整合到竞争相互作用的图景中。特别是，它的目标是了解吸附物(S和GT；1/2)的较高自旋态、磁各向异性或与近邻的交换作用如何影响磁基态和激发态。这一认识不仅具有根本的意义，而且对于实现自旋电子器件的磁性纳米结构也具有重要意义。

In the framework of this proposal we will resolve the basic interaction mechanisms of atomic and molecular spins with a superconducting substrate at the atomic scale. The magnetic moment of the adsorbates couples via exchange interaction to the conduction electrons and Cooper pairs of the substrate. On the one hand, this leads to the screening of the magnetic moment via the so-called Kondo effect and, on the other hand, to a change in the pairing energy of the Cooper pairs, which is reflected in Shiba states inside the superconducting energy gap. The competition of these processes yields a complex many-body state, which we will resolve using scanning tunneling spectroscopy. In a previous work, we could experimentally demonstrate a universal correlation between the efficiency of Kondo screening and the energy of Shiba states in spin-1/2 systems, which has been predicted by theory decades ago. With these results, it also became evident that tiny differences in the atomic environment critically influence the resulting magnetic ground state. We will now increase the complexity of the spin systems and of their environment in order to integrate further factors into the picture of competing interactions. In particular, it is the goal to understand, how higher spin states of the adsorbates (S>1/2), magnetic anisotropy or exchange interactions to nearest neighbors influence the magnetic ground state and excited states. This understanding is not only of fundamental interest, but also important for realizing magnetic nanostructures for spintronic devices.