Single-crystal study of the charge density wave metal LuNiC2

Article

关键词: MAGNETIC-PROPERTIES;    TERNARY CARBIDES;    RNIC2 COMPOUNDS;    RARE-EARTH;    HEAT;   

DOI  :  10.1103/PhysRevB.97.205115

来源: SCIE

【 摘 要 】

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 similar or equal to 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, gamma(CDW)(DFT) = 0.90 mJ/mol K-2, reaches reasonable agreement with the experimental value gamma = 0.83(5) mJ/mol K-2 of LuNiC2. LuCoC2 displays a simplemetallic behavior with neither CDW ordering nor superconductivity above 0.4 K. Its experimental Sommerfeld coefficient, gamma = 5.9(1) mJ/mol K-2, is in realistic correspondence with the calculated, bare Sommerfeld coefficient, gamma(DFT) = 3.82 mJ/mol K-2, of orthorhombic LuCoC2.

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