arXiv subjects

B. Moritz

Publications and source records attributed to B. Moritz.

75 records · Page 5Linked to original sources

arXiv2009

Evidence for weak electronic correlations in Fe-pnictides

Using x-ray absorption and resonant inelastic x-ray scattering, charge dynamics at and near the Fe $L$ edges is investigated in Fe pnictide materials, and contrasted to that measured in other Fe compounds. It is shown that the XAS and RIXS spectra for 122 and 1111 Fe pnictides are each qualitatively similar to Fe metal. Cluster diagonalization, multiplet, and density-functional calculations show that Coulomb correlations are much smaller than in the cuprates, highlighting the role of Fe metallicity and strong covalency in these materials. Best agreement with experiment is obtained using Hubbard parameters $U\lesssim 2$eV and $J\approx 0.8$eV.

cond-mat.supr-con↗

arXiv2007

Charge Density Wave Driven Ferromagnetism in the Periodic Anderson Model

We demonstrate the existence of ferromagnetism in the Periodic Anderson Model (PAM) at conduction-band filling near a quarter. We show that this ferromagnetism is not supported by Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions but is instead driven by the precursors of charge density wave (CDW) formation in the conduction electron band. To study the effect of spatial correlations, we compare Dynamical Mean field Approximation (DMFA) and Dynamical Cluster Approximation (DCA) results. We find that both RKKY and CDW driven ferromagnetism persist as short-range correlations are incorporated into the theory. Both DMFA and DCA show the precursors of CDW formation through the strong enhancement of the d-electron CDW susceptibility as the temperature decreases, up to the ferromagnetic transition temperature. In addition, the DCA captures the signal of a band gap opening due to Peierls instability.

cond-mat.str-el↗

arXiv2007

Cu $K$-edge Resonant Inelastic X-Ray Scattering in Edge-Sharing Cuprates

We present calculations for resonant inelastic x-ray scattering (RIXS) in edge-shared copper oxide systems, such as CuGeO$_{3}$ and Li$_{2}$CuO$_{2}$, appropriate for hard x-ray scattering where the photoexcited electron lies above oxygen 2p and copper 3d orbital energies. We perform exact diagonalizations of the multi-band Hubbard and determine the energies, orbital character and resonance profiles of excitations which can be probed via RIXS. We find excellent agreement with recent results on Li$_{2}$CuO$_{2}$ and CuGeO$_{3}$ in the 2-7 eV photon energy loss range.

cond-mat.str-el↗