Eur. Phys. J. B 63, 11-16 (2008)
https://doi.org/10.1140/epjb/e2008-00205-y

Optical properties of the charge-density-wave polychalcogenide compounds R ₂Te ₅ (R=Nd, Sm and Gd)

¹ Laboratorium für Festkörperphysik, ETH – Zürich, 8093 Zürich, Switzerland
² Geballe Laboratory for Advanced Materials and Department of Applied Physics, Stanford University, Stanford, California, 94305-4045, USA

Corresponding author: ^a degiorgi@solid.phys.ethz.ch

Received: 13 December 2007
Revised: 14 April 2008
Published online: 30 May 2008

Abstract

We investigate the rare-earth polychalcogenide R₂Te₅ (R=Nd, Sm and Gd) charge-density-wave (CDW) compounds by optical reflectivity measurements. We obtain the optical conductivity through Kramers-Kronig transformation of the reflectivity spectra. From the real part of the optical conductivity we then extract the excitation energy of the CDW gap and estimate the fraction of the Fermi surface which is gapped by the formation of the CDW condensate. In analogy to previous findings on the related RTe_n (n=2 and 3) families, we establish the progressive closing of the CDW gap and the moderate enhancement of the metallic component upon chemically compressing the lattice.