Chatzopoulos Damianos, Cho Doohee, Bastiaans Koen M, Steffensen Gorm O, Bouwmeester Damian, Akbari Alireza, Gu Genda, Paaske Jens, Andersen Brian M, Allan Milan P
Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, Leiden, CA, 2333, The Netherlands.
Department of Physics, Yonsei University, Seoul, 03722, Republic of Korea.
Nat Commun. 2021 Jan 12;12(1):298. doi: 10.1038/s41467-020-20529-x.
By using scanning tunneling microscopy (STM) we find and characterize dispersive, energy-symmetric in-gap states in the iron-based superconductor FeTeSe, a material that exhibits signatures of topological superconductivity, and Majorana bound states at vortex cores or at impurity locations. We use a superconducting STM tip for enhanced energy resolution, which enables us to show that impurity states can be tuned through the Fermi level with varying tip-sample distance. We find that the impurity state is of the Yu-Shiba-Rusinov (YSR) type, and argue that the energy shift is caused by the low superfluid density in FeTeSe, which allows the electric field of the tip to slightly penetrate the sample. We model the newly introduced tip-gating scenario within the single-impurity Anderson model and find good agreement to the experimental data.
通过使用扫描隧道显微镜（STM），我们在铁基超导体FeTeSe中发现并表征了色散的、能量对称的能隙态，该材料表现出拓扑超导的特征，以及涡旋核心或杂质位置处的马约拉纳束缚态。我们使用超导STM针尖来提高能量分辨率，这使我们能够表明杂质态可以通过改变针尖-样品距离在费米能级上下进行调控。我们发现杂质态属于汤川-芝-鲁西诺夫（YSR）类型，并认为能量移动是由FeTeSe中低的超流密度引起的，这使得针尖的电场能够轻微穿透样品。我们在单杂质安德森模型中对新引入的针尖栅控情况进行了建模，并发现与实验数据吻合良好。
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