Point-contact spectroscopy of the normal state excitations in PrOs4Sb12

Abstract Point-contact (PC) investigations of the heavy-fermion (HF) superconductor PrOs 4 Sb 12 in the temperature range between 1.5 and 4.2 K and in a magnetic field up to 8 T are presented. The main feature in PC spectra, the second derivative of the I – V curves, in the normal state is a peak at about 1–3 mV. This low-energy peak is smeared by the temperature rise and suppressed (or splitted) by a magnetic field. The origin of the peak is likely excitation of the Pr 3 + ion from the ground Γ 1 state to the upper Γ 5 state, considering the generally accepted crystalline electric field (CEF) schema in PrOs 4 Sb 12 . Absence of the visible features of other CEF transitions in the PC spectra testifies to the dominant coupling of the conducting electrons with this low-lying (about 1 meV in energy) excitation. Thus, this interaction is important for the ascertainment of the nature of HF and superconducting state in PrOs 4 Sb 12 .