Zeeman effects on Yu-Shiba-Rusinov states
Zeeman effects on Yu-Shiba-Rusinov states
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DOI：
10.1103/physrevresearch.4.033182
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发表时间：
2022-08
影响因子：
4.2
通讯作者：
T. Machida;Y. Nagai;T. Hanaguri
中科院分区：
文献类型：
--
作者：
T. Machida;Y. Nagai;T. Hanaguri
当杂质自旋与流动准粒子自旋之间的交换相互作用足够强或足够弱时，超导体中磁性杂质的基态分别为屏蔽自旋或自由自旋。在这两种情况下，最低激发态都是超导间隙内的束缚态，称为Yu-Shiba-Rusinov （YSR）态。YSR态具有空间定域、能量隔离和完全自旋极化的特性，可用于功能扫描探针等领域。虽然任何应用都需要确定杂质自旋是否被屏蔽或自由，但合适的实验技术一直难以捉摸。在这里，我们展示了一种明确的方法来确定杂质基态使用塞曼效应。我们对Cu（111）表面与单磁性铁原子修饰的超导Nb尖端之间形成的结进行了超低温扫描隧道光谱分析。根据Fe吸附物的条件，光谱中的YSR峰在磁场中分裂或移位，分别表明Fe自旋被屏蔽或自由。我们的观察结果为磁性和超导性之间的竞争提供了新的见解，并为YSR态的应用奠定了基础。
When the exchange interaction between the impurity spin and the spins of itinerant quasiparticles are strong or weak enough, the ground states for a magnetic impurity in a superconductor are the screened or free spins, respectively. In both cases, the lowest excited state is a bound state within the superconducting gap, known as the Yu-Shiba-Rusinov (YSR) state. The YSR state is spatially localized, energetically isolated, and fully spin-polarized, leading to applications such as functional scanning probes. While any application demands identifying whether the impurity spin is screened or free, a suitable experimental technique has been elusive. Here we demonstrate an unambiguous way to determine the impurity ground state using the Zeeman effect. We performed ultra-low temperature scanning tunneling spectroscopy of junctions formed between a Cu(111) surface and superconducting Nb tips decorated by single magnetic Fe atoms. Depending on the condition of the Fe adsorbate, the YSR peak in the spectrum either splits or shifts in a magnetic field, signifying that the Fe spin is screened or free, respectively. Our observations provide renewed insights into the competition between magnetism and superconductivity and constitute a basis for the applications of the YSR state.