Broad-based experimental evidence for a hidden phase of cuprate coexistence with far-reaching implications

Analyses of experimental data in the literature show thresholds that directly imply a coexistent superconductive (SC) and pseudogap (PG) phase that, to our knowledge, has not been previously identified. The data used emphasize the essences of d-wave cuprate SC, i.e., the superfluid density and the momentum dependence. For severe underdoping, these data imply that SC condenses conventionally onto the unaltered low-energy density-of-states of a high-temperature PG. Beyond a doping threshold, the high-temperature normal state is replaced, below the SC transition temperature, by a single energetically-favorable thermodynamic phase that embodies a more complex interplay of these orders. This previously hidden phase occupies a central portion of the SC dome, enhances the superfluid density by a factor of two or more to benefit applications, can resolve thirteen mysteries in the literature and suggests an alternative approach to cuprate SC.