Optical study of charge instability in CeRu2Al10 in comparison with CeOs2Al10 and CeFe2Al10

TL;DR

This study investigates the anisotropic electronic structure of CeRu2Al10 and related compounds, revealing how different hybridization strengths and nesting properties contribute to charge-density wave formation and magnetic ordering.

Contribution

It provides a detailed optical and spectroscopic analysis showing the relationship between hybridization, nesting, and magnetic transitions in Ce-based Al compounds.

Findings

CeRu2Al10 has a Kondo semiconductor structure in the ac plane.

Nesting occurs along the b axis below 32 K, slightly above T0.

Weaker c-f hybridization correlates with magnetic ordering.

Abstract

The anisotropic electronic structure responsible for the antiferromagnetic transition in CeRu$_2$Al$_{10}$ at the unusually high temperature of $T_0$ = 28 K was studied using optical conductivity spectra, Ce 3d X-ray photoemission spectra, and band calculation. It was found that the electronic structure in the $ac$ plane is that of a Kondo semiconductor, whereas that along the b axis has a nesting below 32 K (slightly higher than $T_0$). These characteristics are the same as those of CeOs$_2$Al$_{10}$ [S. Kimura {\it et al.}, Phys. Rev. Lett. 106, 056404 (2011).]. The $c$-$f$ hybridization intensities between the conduction and $4f$ electrons of CeRu$_2$Al$_{10}$ and CeOs$_2$Al$_{10}$ are weaker than that of CeFe$_2$Al$_{10}$, showing no magnetic ordering. These results suggest that the electronic structure with one-dimensional weak $c$-$f$ hybridization along the b axis combined with two-dimensional strong hybridization in the $ac$ plane causes charge-density wave (CDW) instability, and the CDW state then induces magnetic ordering.