Comment on ''Valence-band states in Bi2(Ca,Sr,La)3Cu2O8''

In a recent paper, Wells et al. conclude from angle-resolved photoemission spectroscopy that the electronic states at the Fermi energy (EF) of Bi2(Ca,Sr,La)3Cu2O8 have mainly O 2px and 2py symmetry, while O 2pz-like states are not permitted by symmetry at EF. I point out here a deficiency in Wells' et al. symmetry analysis which, when corrected, allows for a significant O 2pz contribution at EF. The resultant degenerate O pz--O pz ''resonant π bonds'' at EF parallel to the Cu-O a-b planes, promoted by significant Cu dxz,yz--O pz π*-antibonding hybridization, along with their associated shallow ''double-well'' potentials, are the basis for a dynamic Jahn-Teller mechanism of high-Tc superconductivity in cuprates