Direct correlation between Tc and CuO2 bilayer spacing in YBa2Cu3O7-x -: art. no. 134517

We report the effects of epitaxial strain and deoxygenation on high quality [YBa2Cu3O7-x(YBCO)(N)/PrBa2Cu3O7(PBCO)(5)](1000 Angstrom) superlattices, with 1 < N < 12 unit cells. High-spatial-resolution electron energy loss spectroscopy shows that strained, fully oxygenated YBCO layers are underdoped. Irrespective of whether underdoping is induced by strain or deoxygenation, x-ray diffraction analysis shows that T-c correlates directly with separation of the CuO2 bilayers.