Anomalies in the Fermi surface and band dispersion of quasi-one-dimensional CuO chains in the high-temperature superconductor YBa2Cu4O8

Visualizing the unusual spectral weight transfer in DyBa2Cu3O7-δ thin film

We report a Spectroscopic Imaging Scanning Tunneling Microscopy (SI-STM) study of a DyBa₂Cu₃O_7-δ (DBCO) thin film (T_c ~ 79 K) synthesized by the molecular beam epitaxy (MBE). We observed an unusual transfer of spectral weight in the local density of states (LDOS) spectra occurring only within the superconducting gap. By a systematic control of the tip-sample distance and the junction resistance, we demonstrate that the spectral weight transfer can be switched at a nano-meter length scale. These results suggest that an interaction between the STM tip and the sample alters the electronic configurations in the film. This probably originates from a combination of an intrinsic band bending at the interface between the surface and the bulk, and a tip-induced band bending. These results may open a new avenue for band engineering and applications of thin films of high-T_c cuprates.