Vacancy Glasses in High T sub c Superconductors

Strong vacancy-vacancy interactions in Y Ba sub 2 Cu sub 3 O sub 7 O sub 2 can explain T sub c ~90K compared to T sub c ~35K in La sub 1.85 Sr sub 0.15 Cu O sub 4 , where Fermi-surface nesting is the dominant mechanism. these vacancy interactions may be observable in the far infrared near 10 micron.