Heavy fermion superconductivity in the filled skutterudite compound PrOs4Sb12

Abstract

The filled skutterudite compound Pr4Sb12 exhibits superconductivity, with a superconducting critical temperature Tc ≈ 1.85 K, that appears to involve heavy fermion quasiparticles with an effective mass m* ≈ 102me, where me is the free electron mass. Evidence for the heavy fermion state in PrOs4Sb 12, based on electrical resistivity, specific heat, and magnetic susceptibility measurements in the normal and superconducting states, is reviewed. New measurements are presented that reveal that Te decreases linearly with pressure to ∼ 20 kbar, the normal state resistivity decreases with decreasing temperature below ∼ 1 - 2 K as a power law T n with n ∼ 3 - 2.6 in magnetic fields from 30 to 80 kOe, and there is structure in the specific heat jump at Tc, suggesting that there are two distinct superconducting phases. Inelastic neutron scattering measurements are consistent with a Pr3+ energy level scheme in the cubic crystalline electric field with a f3 nonmagnetic doublet ground state that carries an electric quadrupole moment, in excellent overall agreement with the Pr3+ energy level scheme inferred from the magnetic susceptibility and specific heat measurements . © 2002 The Physical Society of Japan.