Figure 1: The effect of hydrogen doping on the superconducting transitions of three types of stage 1 KHg-GIC's. (a) Tc increases from 0.85 K to 1.51 K, and delta Tc decreases from 0.035 K to 0.011 K. (b) Tc remains constant at 1.53 K, and delta Tc decreases the same amount as in (a). (c) Tc increases from 1.32 K to 1.49 K, and delta Tc decreases from 0.25 K to 0.03 K.
Figure 2: Schematic model for the density of states in (a) undoped and (b) hydrogenated stage 1 KHg-GIC's. (a) N(Ef) for an undoped compound with Tc less than 1.5 K. Ef lies above the maximum in the density of states in the intercalate bands. (b) N(Ef) for the hydrogen-doped KHg-GIC. The transfer of electrons from intercalate-derived bands to hydrogen levels has lowered the Fermi energy and increased N(Ef).