New insights into cuprate superconductivity and pseudogap by STM of BSCCO

Using a new fitting method which enables us to extract k-space information from STM spectroscopy, we have obtained spatially dependent measurements of the superconducting gap and pseudogap structure as a function of temperature and doping in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ (Bi-2212) and Bi$_{2}$Sr$_{2}$CuO$_{6+x}$ (Bi-2201). These results confirm our previous picture of spatially homogeneous superconductivity with a gap that closes at T$_{C}$ coexisting with an inhomogeneous pseudogap [1]. They also highlight the particle-hole asymmetry of the pseudogap. This, when combined with local measurements of the checkerboard charge order, which we have attributed to a charge density wave [2], provides new insight into the nature of the pseudogap state. [1] Boyer \textit{et al}, \textit{Nat. Phys.} \textbf{3}, 802 (2007) [2] Wise \textit{et al}, \textit{Nat. Phys.} \textbf{4}, 696 (2008)~; \textit{Nat. Phys.} \textbf{5}, 213 (2009)~