Point-contact spectroscopy of the normal state excitations in PrOs4Sb12

TL;DR

This study uses point-contact spectroscopy to investigate the normal state excitations in PrOs4Sb12, revealing a low-energy peak linked to crystal electric field excitations that influence its heavy-fermion and superconducting properties.

Contribution

It provides the first detailed analysis of the normal state excitations in PrOs4Sb12 using point-contact spectroscopy, highlighting the role of low-energy crystal electric field excitations.

Findings

Peak at 1-3 mV in spectra linked to Pr^3+ ion excitation

Peak is suppressed or split by magnetic field

Coupling with low-lying excitation influences heavy-fermion behavior

Abstract

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 Pr^3+ ion from the ground $\Gamma_1$ state to the upper $\Gamma_5$ 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 ascertainment of the nature of HF and superconducting state in PrOs4Sb12.