Vacancies, disorder-induced smearing of the electronic structure, and its implications for the superconductivity of anti-perovskite MgC${}_{0.93}$Ni${}_{2.85}$

Abstract

The anti-perovskite superconductor MgC${}_{0.93}$Ni${}_{2.85}$ was studied using high-resolution x-ray Compton scattering combined with electronic structure calculations. Compton scattering measurements were used to determine experimentally a Fermi surface that showed good agreement with that of our supercell calculations, establishing the presence of the predicted hole and electron Fermi surface sheets. Our calculations indicate that the Fermi surface is smeared by the disorder due to the presence of vacancies on the C and Ni sites, but does not drastically change shape. The 20\% reduction in the Fermi level density-of-states would lead to a significant ($\sim 70\%$) suppression of the superconducting $T_c$ for pair-forming electron-phonon coupling. However, we ascribe the observed much smaller $T_c$ reduction at our composition (compared to the stoichiometric compound) to the suppression of pair-breaking spin fluctuations.

arXiv comment11 pages, 3 figures

References in corpus (23)

• The Electronic Nature of High Temperature Cuprate Superconductors
• Superconductivity Near Ferromagnetism in MgCNi3
• Electronic structures of antiperovskite superconductors: MgXNi${}_3$ (X=B,C,N)
• Superconductivity and Electronic Structure of Perovskite MgCNi3
• Experimental determination of superconducting parameters for the intermetallic perovskite superconductor ${\text {MgCNi}}_3
• (13)C NMR investigation of the superconductor MgCNi_3 up to 800K
• BCS-like Superconductivity in MgCNi3
• Electronic structure, magnetism and superconductivity of MgCNi${}_3$
• Evidence for strong electron-phonon coupling in MgCNi_3
• Carbon Concentration Dependence of the Superconducting Transition Temperature and Structure of MgCxNi3
• Evidence for Unconventional Superconductivity in the Non-Oxide Perovskite $\mathrm{MgCN}{\mathrm{i}}_3$ from Penetration Depth Measurements
• Normal state resistivity, upper critical field and Hall effect in superconducting perovskite $MgCN{i}_3$
• Superconductivity near the vibrational mode instability in MgCNi3
• Observation of a strongly nested Fermi surface in the shape-memory alloy Ni[0.62]Al[0.38]
• Carbon isotope effect in superconducting MgCNi_3
• Influence of Carbon Concentration on the Superconductivity in MgCxNi3
• Thermopower and thermal conductivity of superconducting perovskite $MgCN{i}_3$
• Calculating electron momentum densities and Compton profiles using the linear tetrahedron method
• Photoemission and x-ray absorption study of MgC_(1-x)Ni_3
• Competition between the BCS superconductivity and ferromagnetic spin fluctuations in MgCNi${}_3$
• S-wave superconductivity probed by measuring magnetic penetration depth and lower critical field of MgCNi${}_3$ single crystals
• Conventional superconductivity and hysteretic Campbell penetration depth in single crystals MgCNi${}_3$
• Superconducting energy gap in MgCNi3 single crystals: Point-contact spectroscopy and specific-heat measurements

Cited by in corpus (4)

• Crystal growth, characterization and advanced study of the noncentrosymmetric superconductor Mo${}_3$Al${}_2$C
• High-pressure growth and characterization of bulk MnAs single crystals
• Crystal growth and characterization of the antiperovskite superconductor MgC1-xNi3-y
• Magnetic Compton profiles of Ni beyond the one-particle picture: numerically exact and perturbative solvers of dynamical mean-field theory