The antipressure effect of Cu on T_c in superconducting La(Ni_1−xCu_x)C₂ (0≤x≤0.25)

Abstract

As observed with x-ray powder diffraction, the orthorhombic structure of the parent compound LaNiC2 is retained in La(Ni1−xCux)C2 up to the solubility limit near x = 0.2. The refined lattice parameters show that both the c-axis and the volume of the unit cell v expand clearly, while the a- and b-axes show less percentage change due to doping with copper. These results are inconsistent with what one would expect from a chemical pressure effect. The change in Tc with x is similar to the change in the lattice parameters (c and v) with x and is consistent with the assumption that Cu has finite solubility in this system. Magnetic measurements indicate that the increase in Tc is initially rapid (dTc/dx = 12 K) but slows down (dTc/dx = 1 K) for x≥0.2 in the system La(Ni1−xCux)C2. As expected from the BCS theory, the Cu doping in this system may affect not only the density of state N(EF), but also the electron–phonon coupling parameter.

Superconductivity in Zr2(Co1−xCux)

“…In this paper, we examine the effect of Cu substitution in polycrystals of Zr 2 Co. It is worth noting that Cu substitutions on the magnetic ion Ni site in both the Y(Ni 2Àx Cu x )B 2 C 2 and La(Ni 1Àx Cu x )C 2 systems had ever produced significant effects [9,10] on the superconductivity.…”

Superconductivity in the vicinity of ferromagnetism in oxygen free perovskite MgCNi3: An experimental and density functional theory study

“…For example Ni being coordinated with Carbon in MgCNi 3 [3][4]7] and LaNiC 2 [9] superconductors possesses nearly no magnetic moment. The observance of superconductivity in Ni based compounds is not unprecedented and already reported for the quaternary borocarbides (RENi 2 B 2 C) [7], MgCNi 3 [3][4]7], LaNiC 2 [9] and binary alloy of Bi and Ni (Bi 3 Ni) [10,11] etc. One of the moot questions in regards to MgCNi 3 superconductor is about the nature of its magnetism.…”

Relativistic analysis of the pairing symmetry of the noncentrosymmetric superconductorLaNiC2

“…13,14 At the time, however, the lack of inversion symmetry was largely overlooked. In contrast, very recently there has been a surge of experimental 11,15,16 and theoretical 11,[17][18][19] work on this system. Some of this has been motivated by the results in Ref.…”

“…In addition to this dramatic dependences of T c on Cu, Y, and Th doping have been identified. 15,16,20,21 Two broad and mutually exclusive scenarios have been proposed to describe the breaking of TRS in the superconducting state of LaNiC 2 . 11,19 In the first scenario, which is based on group-theoretical considerations, 11 the superconducting order parameter is intrinsically unconventional: a nonunitary triplet pairing state.…”