Lehrstuhl für Angewandte Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstrasse 7, D-91058 Erlangen, Germany.
Nat Nanotechnol. 2013 Aug;8(8):575-9. doi: 10.1038/nnano.2013.133. Epub 2013 Jul 14.
Single-molecule spintronics investigates electron transport through magnetic molecules that have an internal spin degree of freedom. To understand and control these individual molecules it is important to read their spin state. For unpaired spins, the Kondo effect has been observed as a low-temperature anomaly at small voltages. Here, we show that a coupled spin pair in a single magnetic molecule can be detected and that a bias voltage can be used to switch between two states of the molecule. In particular, we use the mechanically controlled break-junction technique to measure electronic transport through a single-molecule junction containing two coupled spin centres that are confined on two Co(2+) ions. Spin-orbit configuration interaction methods are used to calculate the combined spin system, where the ground state is found to be a pseudo-singlet and the first excitations behave as a pseudo-triplet. Experimentally, these states can be assigned to the absence and occurrence of a Kondo-like zero-bias anomaly in the low-temperature conductance data, respectively. By applying finite bias, we can repeatedly switch between the pseudo-singlet state and the pseudo-triplet state.
单分子自旋电子学研究了通过具有内部自旋自由度的磁性分子的电子输运。为了理解和控制这些单个分子，读取它们的自旋状态很重要。对于不成对的自旋，在小电压下观察到了低温反常现象，即近藤效应。在这里，我们表明可以检测到单个磁性分子中的耦合自旋对，并且可以使用偏置电压在分子的两个状态之间进行切换。具体来说，我们使用机械控制的断键技术测量了包含两个耦合自旋中心的单个分子结中的电子输运，这两个自旋中心被限制在两个 Co(2+)离子上。自旋轨道组态相互作用方法用于计算组合自旋系统，其中基态被发现是一个准单重态，而第一激发态表现为准三重态。实验上，可以将这些状态分别分配给低温电导数据中近藤样零偏压反常的不存在和出现。通过施加有限偏压，我们可以在准单重态和准三重态之间反复切换。
