Observation of Multi-Stage Superconducting Gap States in Bi2Sr2CaCu2OxCrystal Surface by LT-STM/STS

This is the authors' abstract. We don't add key points for this paper.

Low temperature STM/STS observation for BSCCO single crystal was carried out to investigate an intrinsic superconducting gap state of CuO 2 layer. The STM observation revealed out a mid-level-layer between the top and bottom BiO surfaces of the half unit cell in the crystal c-axis direction. The STS study on this mid-level surface brought a reproducible definite superconducting gap structure which shows a finite gap region with a low conductance level of about 5%, and which also shows a nature of wide range gap parameter of Δ max /Δ min ∼4 with Δ min ∼10 meV. This definite gap structure is considered to be a more direct reflection of the superconducting electronic states of the CuO 2 layer than the superconducting gap structure observed at the top BiO layer.