Origin of the Heavy Fermion Behavior in Ca_{2-x}Sr_{x}RuO_{4}: Roles of Coulomb Interaction and the Rotation of RuO_{6} octahedra

Abstract

We study the electronic states for Ca_{2-x}Sr_{x}RuO_{4} in $0.5\le x\le 2$ within the Gutzwiller approximation (GA) on the basis of the three-orbital Hubbard model for the Ru t_{2g} orbitals. The main effects of the Ca substitution are taken account as the changes of the $dp$ hybridizations between the Ru 4d and O 2p orbitals. Using the numerical minimization of the energy obtained in the GA, we obtain the renormalization factor (RF) of the kinetic energy and total RF, which estimates the inverse of the mass enhancement, for three cases with the effective models of x=2 and 0.5 and a special model. We find that the inverse of the total RF becomes the largest for the case of x=0.5, and that the van Hove singularity, which is located on (below) the Fermi level for the special model (the effective model of x=0.5), plays a secondary role in enhancing the effective mass. Our calculation suggests that the heavy fermion behavior around x=0.5 comes from the cooperative effects between moderately strong Coulomb interaction compared to the total bandwidth and the modification of the electronic structures due to the rotation of RuO_{6} octahedra (i.e., the variation of the $dp\pi$ hybridizations and the downward shift for the $d_{xy}$ orbital). We propose that moderately strong electron correlation and the orbital-dependent modifications of the electronic structures due to the lattice distortions play important roles in the electronic states for Ca_{2-x}Sr_{x}RuO_{4}.

16 pages, 13 figures, 1 table, accepted for publication in Physical Review B; added the discussions both about the validity of the present treatment and about Hund's metal in this alloy

References in corpus (6)

• Effect of Structural Parameters on Superconductivity in Fluorine-Free LnFeAsO1-y (Ln=La,Nd)
• Coherence-incoherence crossover in the normal state of iron-oxypnictides and importance of the Hund's rule coupling
• The coherence-incoherence crossover and the mass-renormalization puzzles in Sr2RuO4
• Mott Transitions and d-wave Superconductivity in Half-Filled-Band Hubbard Model on Square Lattice with Geometric Frustration
• Electronic structures of layered perovskite Sr2MO4 (M=Ru, Rh, and Ir)
• Subband filling and Mott transition in Ca_{2-x}Sr_xRuO_4

Cited by in corpus (2)

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