Highlights 2013
Excitation Spectrum in Ni- and Cu-doped ZrTe3
ZeTe3 belongs to the ample class of chain-like chalcogenide charge-density-wave (CDW) materials. Ni and Cu intercalation of ZrTe3 leads to the onset of bulk superconductivity at Tc < TCDW, raising questions about the possible coexistence as well as competition between both broken-symmetry ground states. We optically investigate Ni0.05ZrTe3 and Cu0.05ZrTe3 single crystals with electromagnetic radiation polarized along the in-plane crystallographic a and b axes, over a broad spectral range and as a function of temperature. The charge dynamics of the CDW state displays a polarization dependence within the ab-plane and gives evidence for a partial gapping of the Fermi surface, which affects almost exclusively the crystallographic direction parallel to the a-axis.
We provide a complementary analysis of the spectral weight distribution, disentangling its reshuffling in the excitation spectrum across the symmetry-breaking CDW transition. While the superconducting energy gap lies outside our measurable spectral range, we observe nonetheless that the CDW-gap feature persists at T < Tc. We propose that CDW and superconductivity coexist along the a-axis.