Cryogenic Scanning Tunneling Microscopy and Spectroscopy on the Cleaved Surface of Bi-Sr-Ca-Cu-O Down to 4.2 K

Abstract

Atomic resolution has been achieved by a scanning tunneling microscopy (STM) system for the first time on an oxide superconductor at cryogenic temperatures. The atomic corrugation with a periodicity of 0.35 nm and the modulation along the b-axis with a superlattice periodicity of about 2.7 nm have both been clearly observed on the cleaved a-b plane of a Bi-Sr-Ca-Cu-O single crystal. Furthermore, it is found that some features of the spectrum, including the shape of the superconducting gap, depended significantly on the distance between the probe tip and sample surface. Wide scattering of the results so far reported for various types of tunneling methods can be interpreted in terms of this distance dependence of the tunneling spectrum. We conclude that the superconducting gap structure in the spectrum is by far different from the prediction of the BCS weak-coupling theory.

Scanning tunneling spectroscopy of high-temperature superconductors

“…Only low-resistance tunnel junctions (R t ∼ MΩ), i.e. when the tip is in very close proximity to the surface, allowed to measure superconducting gap features on Bi2212 and Y123 (Aleszkiewicz et al, 1997;Hasegawa et al, 1991aHasegawa et al, , 1992Nantoh et al, 1994b). Upon increasing the junction resistance (R t ∼ GΩ) by pulling the tip away from the surface, these superconducting features vanished and the tunneling spectra evolved into semiconducting-like line shapes.…”

Eliashberg Analysis of Tunneling Experiments: Support for the Pairing Glue Hypothesis in Cuprate Superconductors

“…A states conserving normalization of low leakage SIS conductance spectra [18] is used in this analysis. We take advantage of a number of studies [19][20][21] that show clearly that the normal state conductance is a smoothly varying function which merges with the superconducting conductance for voltages just beyond that of the hump in the dip or hump spectral feature.…”

Scanning Tunneling Microscopy and Surface Simulation of Zinc-Blende GaN(001) Intrinsic4×Reconstruction: Linear Gallium Tetramers?

“…Based on both fundamental and technological motivations, reconstructions occurring on almost every metal, semiconductor, superconductor, and even certain oxide, surfaces have been investigated and imaged directly with scanning tunneling microscopy (STM) [1][2][3]. In particular, reconstructions of the (001) surfaces of III-V semiconductors have been explored intensively for the past 30 years [4,5].…”