Size-dependent Quantum Diffusion Of Gd Atoms Within Fe Nano-corrals

We performed a systematic study of size-dependent quantum diffusion of Gd atoms within the Fe circular quantum corrals. Inside 6-nm,10-nm and 14-nm quantum corrals, we observe dot, circular and both diffusion orbits for Gd adatoms, respectively. Evolution of LDOS near EF is presented and interaction energy between ad Gd-corral is plotted. With quantitative analysis, we confirm that the regions of minimum in adatom-corral interaction energy correspond to diffusion orbits for adatoms strictly, and they are very closed to the high LDOS with offset of less than 0.2-nm. Moreover, we observed that those surface electrons confined outside have a trapping effect on adatoms walking outside, to form an extra Gd circular corral. In addition, after taking the real geometry of circular corrals into account, KMC simulations well reproduce similar features to experimental result. In detail, we find Fe adatoms’position deviations perpendicular to the radial direction influence the uniformity of diffusion orbits while deviations along the radial direction influence their radius. Inside the 14-nm circular corral with two orbits, we find Gd adatoms prefer to occupy the dot orbit at the center with a higher LDOS and a lower interaction energy minimum. Our systematic study demonstrated that we can engineer adatoms motion or create novel atomic structures actively by designing different-sized quantum corrals.In addition, we created a novel method to build the "Gd inside Fe corral" system. We opened a door by moving one Fe atom away from its position relative to the corral to let Gd adatoms in. By calculating the Gd-Corral interaction energy map, we found there indeed exist an diffusion channel for Gd adatoms to go inside the corral with such a door. This method has been demonstrated to be an simple and efficient way in our experiments and could be used to study novel phenomena in low dimension in the future.