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S. Steiner, H. Michor, O. Sologub, B. Hinterleitner, F. Höfenstock, M. Waas, E. Bauer, B. Stöger, V. Babizhetskyy, V. Levytskyy, B.Ya. Kotur:
"Single-crystal study of the charge density wave metal LuNiC₂";
Physical Review B, 97 (2018), 205115; S. 1 - 11.

We report on single-crystal growth, single-crystal x-ray diffraction, physical properties, and density functional theory (DFT) electronic structure as well as Fermi surface calculations for two ternary carbides, LuCoC₂ and LuNiC₂. Electrical resistivity measurements reveal for LuNiC₂ a charge density wave (CDW) transition at T_CDW= 450 K and, for T >T_CDW, a significant anisotropy of the electrical resistivity, which is lowest along the orthorhombic a-axis. The analysis of x-ray superstructure reflections suggest a commensurate CDW state with a Peierls-type distortion of the Ni atom periodicity along the orthorhombic a axis. DFT calculations based on the CDW modulated monoclinic structure model of LuNiC₂ as compared to results of the orthorhombic parent type reveal the formation of a partial CDW gap at the Fermi level which reduces the electronic density of states from N(E_F) = 1.03 states/eV f.u. without CDW to N(E_F) = 0.46 states/eV f.u. in the CDW state. The corresponding bare DFT Sommerfeld value of the latter, γ_CDW^DFT= 0.90 mJ/molK², reaches reasonable agreement with the experimental value γ = 0.83(5) mJ/molK² of LuNiC₂. LuCoC₂ displays a simple metallic behavior with neither CDW ordering nor superconductivity above 0.4 K. Its experimental Sommerfeld coefficient, γ = 5.9(1) mJ/molK², is in realistic correspondence with the calculated, bare Sommerfeld coefficient, γ^DFT = 3.82 mJ/molK², of orthorhombic LuCoC₂.

Charge density waves, Electronic structure, Fermi surface

http://dx.doi.org/10.1103/PhysRevB.97.205115