Figure 1

Superconducting to normal-state transmission (upper panel) and reflection (lower panel) ratios at 0, 5, and 10 T. The weak oscillatory features are partially resolved multiple internal reflections in the substrate. The upper panel inset is the transmittance for $T=300\mathrm{K}$, measured at $3\times$ higher spectral resolution along with a fit using the optical constants of quartz [13] (blue curve). The inset in the lower panel is a diagram of the reflection sample holder. The sample is the thin black slab near the middle. A polished aluminum roof-type mirror reflects the input beam onto the sample at a 30° angle and then redirects the reflected beam back onto the original optical path.Reuse & Permissions

Figure 2

(a)–(c) The real and imaginary parts of the $T=3\mathrm{K}$ superconducting state optical conductivity (normalized to the normal-state conductivity) at three different applied magnetic fields. The solid lines are fits to ${\sigma }_1/{\sigma }_N$ using the pair-breaking theory. The dashed lines show the corresponding ${\sigma }_2/{\sigma }_N$ as determined by a Kramers-Kronig transform of the real part. (d) The fitted ${\sigma }_1/{\sigma }_N$ at six fields.Reuse & Permissions

Figure 3

Field dependence of the pair-breaking parameter $\Gamma$, determined from the experimental optical conductivity (circles) along with a fit to $\Gamma =b{H}^2$ (solid line). The inset shows the pair-correlation gap $\Delta$ and the effective spectroscopic gap ${\Omega }_G$ vs field. The solid lines are theoretical predictions using the pair-breaking theory and the fitted value of $b$.Reuse & Permissions