Figure 1
From: Phonon engineering in proximity enhanced superconductor heterostructures
(a) Calculated total phonon density of states as a function of phonon energy for 5 nm and 10 nm Al films. The vertical line shows where the gap energy 2Δ(0) for 5 nm Al in the heterostructure is located. The inset illustrates how quasiparticle DOS at T = 1.2 K broadens when θ varies from 10−4 (cyan curve) to 6 × 10−4 (red curve). The vertical line shows where the quasiparticle energy equaling to Δ(0) for 5 nm Al in the heterostructure is located. (b) Calculated superconducting pair potential distribution with depth for 5/50/5 and 10/50/10 nm Al/Nb/Al heterostructure. The dashed line is the gap energy for a single 50 nm Nb layer determined from our experiment. The inset is the schematic illustration of the Al/Nb/Al heterostructure on a double-side-polished c-cut sapphire. The back side is coated with 50 nm Nb.
