Energy gap formation in a valence fluctuating compound CeIrSb probed by Sb NMR and NQR

TL;DR

This study uses Sb NMR/NQR to reveal a large energy gap with a V-shaped profile in CeIrSb, indicating a pseudogap formation due to c-f hybridization, with results consistent across similar compounds.

Contribution

It provides the first detailed characterization of the pseudogap in CeIrSb, showing a larger energy gap compared to related compounds and confirming the V-shaped gap structure.

Findings

Energy gap in CeIrSb is about 350 K.

CeIrSb exhibits a V-shaped pseudogap similar to other Kondo semiconductors.

The temperature dependence of relaxation rates and Knight shift supports pseudogap formation.

Abstract

Sb-NMR/NQR study has revealed a formation of a pseudogap at the Fermi level in the density of states in a valence fluctuating compound CeIrSb. The nuclear spin-lattice relaxation rate divided by temperature, 1/T_1T has a maximum around 300 K and decreases significantly as 1/T_1T ~ T^2, followed by a 1/T_1T = const. relation at low temperature. This temperature dependence of 1/T_1T is well reproduced by assuming a V-shaped energy gap with a residual density of states at the Fermi level. The size of energy gap for CeIrSb is estimated to be about 350 K, which is by one order of magnitude larger than those for the isostructural Kondo semiconductors CeRhSb and CeNiSn. Despite the large difference in the size of energy gap, CeIrSb, CeRhSb and CeNiSn are indicated to be classified into the same group revealing a V-shaped gap due to c-f hybridization. The temperature dependence of the Knight shift measured in a high magnetic field agrees with the formation of this pseudogap.