Low Energy Excitations in the Mixed State of the Anisotropic s-Wave Superconductor CeRu₂

抄録

Angle-resolved specific heat measurements are preformed on the f-electron superconductor CeRu₂ in rotating magnetic fields 0.5≤H≤6 T at various temperatures 0.3≤T≤2 K. In the whole H–T range examined, a clear 4-fold oscillation is observed and yields the gap minimum (maximum) located to ⟨110⟩ (⟨100⟩) in the cubic crystal with the ratio Δ_min⁄Δ_max∼0.3. The oscillation amplitude landscape in H–T plane with a local maximum is explained by a microscopic theory, pointing to a new spectroscopy for gap determination.