Nanostripe structures in as-grown light-rare-earth-based high-Tc superconductors

Nanostripes are visualized on as-grown light-rare-earth-based high-Tc superconductors by means of atomic force microscopy (AFM) and scanning tunnelling microscopy (STM) at ambient conditions. The samples investigated are non-superconducting, and hence, twin-free. Our observations of nanostripe structures in these samples directly proof that the nanostripes are formed during the growth of the 123-phase itself, whereas the twin boundaries appear in a second step during the required oxygenation of the samples. This explains the often observed features that the nanostripes are curved towards or away from the twins. Due to the different length scales, the nanostripes in the LRE-materials are filling effectively the space between the twin boundaries and provide flux pinning sites much closer to the size of the coherence length, ξ.