Band-Resolved Superconducting Gaps via the Thermal Hall Effect in CeRu2
Standard probes cannot assign superconducting gaps to specific Fermi surface sheets because they average over all carriers. This study uses thermal Hall transport ($\kappa_{xy}$) in CeRu2 to resolve this ambiguity. By fixing gap scales using specific heat and mobility ratios, a low-field sign reversal in $\kappa_{xy}$ proves the larger gap is on the heavy Ce 4f electron sheets, while the smaller gap is on hole sheets.