STM/STS study on large pseudogap and nodal superconducting gap in Bi2201(La) and Bi2212

In the present work, scanning tunneling microscopy/spectroscopy (STM/STS) measurements were carried out on underdoped $\rm Bi_2Sr_{2-{\it x}}La_{\it x}CuO_{6+\delta}$ and $\rm Bi_2Sr_2CaCu_2O_{8+\delta}$ to clarify the origin of the pseudogap, in particular, the inhomogeneous large pseudogap. The nodal part of a d-wave pairing gap, which is under no influence of the inhomogeneous large pseudogap, was also examined by relating the homogeneous bottom part of the STS gap to a nodal d-wave gap in momentum space. We report that the inhomogeneous large pseudogap in the antinodal region links to a two-dimensional electronic charge order, and that the gap size of the nodal d-wave part $\rm {\Delta}_{sc}$ scales with the superconducting critical temperature $\rm {\it T}_c$ in the pseudogap regime.