Point-contact spectroscopy of the normal state excitations in PrOs4Sb12

Point-contact (PC) investigations of the heavy-fermion (HF) superconductor PrOs4Sb12 in the temperature range between 1.5 and 4.2K and in a magnetic field up to 8T 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 1–3mV. 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 Pr3+ ion from the ground Γ1 state to the upper Γ5 state, considering the generally accepted crystalline electric field (CEF) schema in PrOs4Sb12. 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 1meV in energy) excitation. Thus, this interaction is important for the ascertainment of the nature of HF and superconducting state in PrOs4Sb12.