An intrinsic Cu-O-Cu bond-centered electronic glass with disperse 4$a_0$-wide unidirectional domains in strongly underdoped Ca$_{1.88}$Na$_{0.12}$CuO$_2$Cl$_2$ and Bi$_2$Sr$_2$Dy$_{0.2}$Ca$_{0.8}$Cu$_2$O$_y$

Hole doping into the CuO$_2$ charge transfer insulator alters the electronic correlations, leading to the high-$T_{\rm c}$ superconductivity (HTS). The correlation alterations are accompanied by spectral weight transfers from the high energy states of the insulator to low energies. Recently, it has been proposed~[1,2] that these effects might be observable as an asymmetry of electron tunneling currents with bias voltage across the chemical potential. Atomic-scale TA-phenomena would then be of crucial importance to understand the fundamental electronic structure of the CuO$_2$ plane from whence the HTS emerges.\par In this talk, we will report the first application of atomic resolution TA-imaging by STM, detecting virtually identical phenomena in two different lightly hole-doped cuprates: Ca$_{1.88}$Na$_{0.12}$CuO$_2$Cl$_2$ and Bi$_2$Sr$_2$Dy$_{0.2}$Ca$_{0.8}$Cu$_2$O$_y$. We find intense spatial variation primarily on planer oxygen sites. Their spatial arrangements appear to be a Cu-O-Cu bond-centered electronic glass, breaking translational symmetry of lattice and 90$^{\circ}$-rotational symmetry. 4$a_0$-wide unidirectional domains ($a_0$: Cu-O-Cu length) are embedded throughout this matrix and running along the both Cu-O bonds without preferred orientation. Relationship to the electronic cluster glass, the bond-centered stripe, and the high-$T_{\rm c}$ superconductivity will be discussed.\par \par This work is done in collaboration with C. Taylor, A. Schmidt, C. Lupien, T. Hanaguri, M. Azuma, M. Takano, K. Fujita, H. Eisaki, H. Takagi, S. Uchida, and J. C. Davis. \par \par [1] P. W. Anderson, N. P. Ong, cond-mat/0405518 \& {\it J. Phys. Chem. Solid} {\bf 67}, 1 (2006).\par [2] M. Randeria, R. Sensarma, N. Trivedi, F. -C. Zhang, {\it Phys. Rev. Lett.} {\bf 95}, 137001 (2005).