Tc oscillations
Tc (black solid dots) and the density of states (red stars) as a function of lead film thickness, demonstrating a nonmonotonic oscillatory behavior in both Tc and the density of states. The inset shows the resistance as a function of temperature measured from the 28-atomic layer film, which reveals a sharp transition to superconductivity at 6.32 K, as indicated by the arrow. (Image and text: Science 306 1915).