Computational materials design of attractive Fermion system with large negative effective U-eff in the hole-doped Delafossite of CuAlO2, AgAlO2 and AuAlO2: Charge-excitation induced U-eff < 0

作者：Nakanishi A; Fukushima T^*; Uede H; Katayama Yoshida H

来源：Physica C-Superconductivity and Its Applications, 2015, 519: 168-183.

DOI：10.1016/j.physc.2015.10.007

• Negative effective U
• Delafossite
• Density functional theory
• Negative U Hubbard model
• Self-interaction correction

On the basis of general design rules for negative effective U(U-eff) systems by controlling purely-electronic and attractive Fermion mechanisms, we perform computational materials design (CMD (R)) for the negative U-eff system in hole-doped two-dimensional (2D) Delafossite CuAlO2, AgAlO2 and AuAlO2 by ab initio calculations with local density approximation (LDA) and self-interaction corrected-LDA (SIC-LDA). It is found that the large negative U-eff in the hole-doped attractive Fermion systems for CuAlO2 (U-eff(LDA)=-4.53 eV and U-eff(SIC-LDA)=-4.20 eV), AgAlO2 (U-eff(LDA)=-4.88 eV and U-eff(SIC-LDA)=-4.55 eV) and AuAlO2 (U-eff(LDA)=-4.14 eV and U-eff(SIC-LDA)=-3.55 eV). These values are 10 times larger than that in hole-doped three-dimensional (3D) CuFeS2 (U-eff=-0.44 eV). For future calculations of T-c and phase diagram by quantum Monte Carlo simulations, we propose the negative U-eff Hubbard model with the anti-bonding single pi-band model for CuAlO2, AgAlO2 and AuAlO2 using the mapped parameters obtained from ab initio electronic structure calculations. Based on the theory of negative U-eff Hubbard model (Nozieres and Schmitt-Rink, 1985), we discuss vertical bar U-eff vertical bar dependence of superconducting critical temperature (T-c) in the 2D Delafossite of CuAlO2, AgAlO2 and AuAlO2 and 3D Chalcopyrite of CuFeS2, which shows the interesting chemical trend, i.e., T-c increases exponentially (T-c proportional to exp[-1/vertical bar U-eff vertical bar]) in the weak coupling regime vertical bar U-eff(-0.44eV)vertical bar<W(similar to 2eV) (where W is the band width of the negative U-eff Hubbard model) for the hole-doped CuFeS2, and then T-c goes through a maximum when vertical bar U-eff(-4.88eV,-4.14eV)vertical bar similar to W(2.8eV, 3.5eV) for the hole-doped AgAlO2 and AuAlO2, and finally T-c decreases with increasing vertical bar U-eff vertical bar in the strong coupling regime, where View the MathML source vertical bar U-eff(-4.53eV)vertical bar>W(1.7eV), for the hole-doped CuAlO2.

• 出版日期2015-12-15