Control of single-spin magnetic anisotropy by exchange coupling
Control of single-spin magnetic anisotropy by exchange coupling
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DOI：
10.1038/nnano.2013.264
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发表时间：
2014-01-01
影响因子：
38.3
通讯作者：
Hirjibehedin, Cyrus F.
中科院分区：
文献类型：
--
作者：
Oberg, Jenny C.;Calvo, M. Reyes;Hirjibehedin, Cyrus F.
量子系统与其环境相互作用的性质，通常称为开放量子系统，可以受到这种相互作用的强烈影响。虽然这可能会导致不必要的后果，例如在用于量子计算的量子比特中引起退相干（1），但它也可以被用作环境的探测器。例如，磁共振成像是基于质子（2）在宿主组织（3）中的水分子中的自旋弛豫时间的依赖性。在这里，我们表明，由磁晶各向异性决定并控制其稳定性和在磁性数据存储设备中使用的适用性的单个自旋的激发能（4）可以通过改变自旋与附近导电电极的交换耦合来修改。使用扫描隧道显微镜和光谱学，我们观察到的变化的两个因素的自旋激发能的单个原子的自旋的耦合到周围的电子浴的变化的强度。这些观察结果，结合计算，表明交换耦合可以强烈修改磁各向异性。因此，这个系统是为数不多的开放量子系统之一，其中的能级，而不仅仅是激发态的寿命，可以可控地重整化。此外，我们证明了磁晶各向异性，通常由自旋周围的局部结构确定的属性，可以电子调谐。这些效应可能在自旋电子器件（5）的发展中发挥重要作用，在自旋电子器件中，单个磁性原子或分子与导电引线耦合。
The properties of quantum systems interacting with their environment, commonly called open quantum systems, can be affected strongly by this interaction. Although this can lead to unwanted consequences, such as causing decoherence in qubits used for quantum computation(1), it can also be exploited as a probe of the environment. For example, magnetic resonance imaging is based on the dependence of the spin relaxation times of protons(2) in water molecules in a host's tissue(3). Here we show that the excitation energy of a single spin, which is determined by magnetocrystalline anisotropy and controls its stability and suitability for use in magnetic data-storage devices(4), can be modified by varying the exchange coupling of the spin to a nearby conductive electrode. Using scanning tunnelling microscopy and spectroscopy, we observe variations up to a factor of two of the spin excitation energies of individual atoms as the strength of the spin's coupling to the surrounding electronic bath changes. These observations, combined with calculations, show that exchange coupling can strongly modify the magnetic anisotropy. This system is thus one of the few open quantum systems in which the energy levels, and not just the excited-state lifetimes, can be renormalized controllably. Furthermore, we demonstrate that the magnetocrystalline anisotropy, a property normally determined by the local structure around a spin, can be tuned electronically. These effects may play a significant role in the development of spintronic devices(5) in which an individual magnetic atom or molecule is coupled to conducting leads.