Competition between spin fluctuations in Ca2-xSrxRuO4 around x=0.5

Article

关键词: TRANSITION SYSTEM CA2-XSR(X)RUO4;    MOTT TRANSITION;    TRIPLET SUPERCONDUCTIVITY;    LAYERED PEROVSKITE;    SR2RUO4;    METALS;   

DOI  :  10.1103/PhysRevB.87.195110

来源: SCIE

【 摘 要 】

We study the static susceptibilities for charge and spin sectors in paramagnetic states for Ca2-xSrxRuO4 in 0.5 <= x <= 2 within random phase approximation on the basis of an effective Ru t(2g) orbital Hubbard model. We find that several modes of spin fluctuation around q = (0,0) and q similar to (0.797 pi,0) are strongly enhanced for the model of x = 0.5. This enhancement arises from the increase of the corresponding susceptibilities for the d(xy) orbital due to the rotation-induced modifications of the electronic structure for this orbital (i.e., the flattening of the bandwidth and the increase of the density of states near the Fermi level). We also find that the ferromagnetic spin fluctuation becomes stronger for a special model than for the model of x = 0.5, while the competition between the modes of spin fluctuation at q = (0,0) and around q = (pi,0) is weaker for the special model; in this special model, the van Hove singularity (vHs) for the d(xy) orbital is located on the Fermi level. These results indicate that the location of the vHs for the d(xy) orbital, which is controlled by substitution of Ca for Sr, is a parameter to control this competition. We propose that the spin fluctuations for the d(xy) orbital around q = (0,0) and q similar to (pi,0) play an important role in the electronic states around x = 0.5 other than the criticality approaching the usual Mott transition where all electrons are localized.

【 授权许可】

Free