J. Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
Phys Rev Lett. 2010 May 14;104(19):196102. doi: 10.1103/PhysRevLett.104.196102.
Using a low-temperature scanning tunneling microscope (STM), we observe that Co adatoms are unusually strongly bound to a particular type of pinning centers on the Cu(111) surface. Using density-functional-theory calculations, the pinning centers are identified as Ag substitutional atoms embedded in the topmost atomic layer of the surface. These impurities are hardly detectable in the STM images as they have low topographic height and produce no standing-wave patterns. They do not affect the exchange coupling of the Co adsorbate with the substrate electrons; thus, the Kondo resonances measured on pinned and free Co adatoms show no detectable differences. Whereas free Co adatoms undergo significant surface diffusion already above 8 K, Ag-stabilized Co adatoms remain pinned up to 12.7 K.
使用低温扫描隧道显微镜（STM），我们观察到 Co 原子吸附物异常强烈地结合到 Cu(111)表面上的一种特殊类型的钉扎中心。使用密度泛函理论计算，钉扎中心被确定为嵌入表面最顶层的 Ag 替代原子。这些杂质在 STM 图像中几乎无法检测到，因为它们的地形高度较低，并且不会产生驻波图案。它们不会影响 Co 吸附物与基底电子的交换耦合；因此，在钉扎和自由 Co 原子吸附物上测量的 Kondo 共振没有可检测到的差异。虽然自由 Co 原子在 8 K 以上就会发生显著的表面扩散，但 Ag 稳定的 Co 原子吸附物在 12.7 K 时仍被钉扎。
