High-resolution angle-resolved photoemission study of incommensurate charge-density-wave compoundCeTe3

Abstract

High-resolution angle-resolved photoemission spectroscopy (ARPES) has been performed on layered cerium trichalcogenide CeTe 3 to study the incommensurate charge-density-wave (CDW) mechanism. We found that ARPES spectra near the Fermi level along the superlattice direction (⌫Y direction) show existence of multiple shadow bands due to the CDW formation, while those along the ⌫X direction perpendicular to ⌫Y do not show such a band folding. The energy dispersion of shadow bands is understood in terms of the momentum transfer due to the periodic lattice distortion vector. The observed sizable CDW gap amplitude ͑Ͼ250 meV͒ around Y point is in accordance with the observation of higher order shadow bands.Single-crystals of CeTe 3 were prepared by a flux method using alkaline metal chloride. 4 Mixture of the element pow-FIG. 1. (a) Crystal structure and (b) Brillouin zone of CeTe 3 .

Chemical pressure and hidden one-dimensional behavior in rare-earth tri-telluride charge-density wave compounds

“…The CDW gap ranges between 200 and 400 meV, depending on the rare earth. [15][16][17][18][19] Consistent with these large gap values, RTe 3 compounds are well within the CDW state already at room temperature and the CDW transition temperature ͑T CDW ͒ is believed to be even higher than the melting point. 17 Owing to the 2D character of these compounds, the gap is not isotropic and shows a wave-vector dependence.…”

“…That a significant part of the FS is gapped in the CDW phase, is confirmed by ARPES data from which the fraction of the ungapped FS can be estimated to be 10-20 %. [15][16][17][18] In this respect, the quantity ⌽ = P 2 / ͑ P 2 + S SP 2 ͒ is of interest, since it represents the ratio between the spectral weight [15][16][17][18] they at least qualitatively confirm that a large portion of FS is gapped. The difference between ARPES and optics, as far as the gapping of FS is concerned, may also be reconciled in part by taking into account the energy resolution of the ARPES data.…”

“…Therefore, the SP peak in each compound can be thought as composed by the superposition of several excitations, which mimic the continuous distribution of gap values, as observed by ARPES. [15][16][17][18][19] The remaining two high frequency HO's account for the optical ͑electronic interband͒ transitions.…”

“…14 This nesting appears to be the driving mechanism for the CDW instability. 15,16 The compounds are characterized by an unusually large CDW gap, which was observed by angle resolved photoemission spectroscopy ͑ARPES͒ measurements. The CDW gap ranges between 200 and 400 meV, depending on the rare earth.…”

“…17 Owing to the 2D character of these compounds, the gap is not isotropic and shows a wave-vector dependence. 16,17 In particular, since the vector q ជ does not nest the whole FS, there are parts of it which are not gapped. Therefore, the CDW state coexists with the metallic phase due to the free charge carriers in the ungapped regions of the FS.…”