Photoemission study of the Kondo insulator Ce ₃ Bi ₄ Pt ₃

Abstract

The electronic structure of the Kondo insulator Ce3Bi4Pt3 has been studied by high-resolution photoelectron spectroscopy. Indications of the unusual electronic structure are observed: the 4f derived peak near the Fermi level is located at a binding energy of 20 meV and is not cut-off by the Fermi edge as in conventional Kondo systems; for low photon energies, where the 4f contribution is negligible and the conduction band states are probed, a loss of spectral intensity in the same energy range is observed. These observations are related to the opening of a gap at low temperature, confirming the picture that hybridisation between a localised 4f state and the conduction band is responsible for the insulating character of this material.

Hybridized Nature of Pseudogap in Kondo Insulators CeRhSb and CeRhAs

“…We find that the peak position in CeRhAs (50 -60 meV) is farther away from E F than in CeRhSb (20-30 meV). A similar depletion of the 4f-spectral intensity near E F has also been reported for Ce 3 Bi 4 Pt 3 [9], indicating that the depletion near E F is a characteristic feature in Kondo insulators. However, one might think that the depletion of the 4f spectral weight is due to a satellite structure from the crystal field (CF) splitting, since the Kondo resonance peak ͑4f 5͞2 ͒ may accompany a CF satellite structure a little away from E F , as observed by PES in CeB 6 [18].…”

“…In Fig. 2, we find that the gap is not a full gap but a pseudogap with a finite DOS at E F , which is a common feature of the "Kondo gap" observed by PES [9][10][11]. This may be due to an extrinsic signal from a possibly metallic surface layer.…”

“…Thus it is important to study the energy gaps and their temperature dependence for a better understanding of the interplay between f and conduction electrons in Kondo insulators. In the highresolution photoemission spectroscopy (HRPES) experiment a pseudogap in the conduction-electron-derived electronic structure in several Kondo insulators was observed [9][10][11]. In contrast, few attempts [9] have been made to observe the counterpart in the f-derived electronic structure, although both gaps are simultaneously formed through the c-f hybridization.…”

“…Here it is worthwhile to comment on the surface contribution to the PES spectra, since the coherence indispensable to the Kondo gap might be disturbed by the smaller hybridization at surface [9,20]. In Fig.…”

A Kondo insulating memristor

“…The heavy fermion compound Ce 3 Bi 4 Pt 3 is a so-called Kondo insulator 8 with a hybridization gap 9 which opens below approximately 100 K. This material has been studied via various experimental methods. [10][11][12][13][14] The electrical resistivity measured at low current shows more than 2 orders of magnitude increase from 300 K to 2 K characterizing a continuous metal insulator transition, as shown in Fig. 1.…”