Fig. 4: Doping dependence of H_c,2 in strained YBCO films.

a Linear fits of \({T}_{c}^{0.5{R}_{N}}(H)\) for films with different values of p. The current is applied along the a-axis. The pink hexagons show the linear extrapolated values of H_c,2 at \({T}_{c}^{0.5{R}_{N}}=0\). The error bars are estimated from the uncertainty of the T=0 value of the linear fits. b Doping dependence of H_c,2 in d = 10 nm (pink hexagons) and d = 50 nm (blue triangles) YBCO films. The blue dashed line shows the doping dependence of H_c,2 measured in YBCO crystals³⁸. c Difference between \({T}_{c}^{on}\) (red squares) and H_c,2 (pink hexagons) in d = 10 nm and d = 50 nm films.