Analysis of spin density wave conductivity spectra of iron pnictides in the framework of density functional theory - Condensed Matter > SuperconductivityReportar como inadecuado




Analysis of spin density wave conductivity spectra of iron pnictides in the framework of density functional theory - Condensed Matter > Superconductivity - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: The optical conductivity of LaFeAsO, BaFe$ 2$As$ 2$, SrFe$ 2$As$ 2$, andEuFe$ 2$As$ 2$ in the spin-density wave SDW state is investigated withindensity functional theory DFT in the framework of spin-polarized generalizedgradient approximation GGA and GGA+U. We find a strong dependence of theoptical features on the Fe magnetic moments. In order to recover the small Femagnetic moments observed experimentally, GGA+$U { m eff}$ with a suitablechoice of negative on-site interaction $U { m eff}=U-J$ was considered. Suchan approach may be justified in terms of an overscreening which induces arelatively small U compared to the Hund-s rule coupling J, as well as a strongHolstein-like electron-phonon interaction. Moreover, reminiscent of the factthat GGA+$U { m eff}$ with a positive $U { m eff}$ is a simple approximationfor reproducing a gap with correct amplitude in correlated insulators, anegative $U { m eff}$ can also be understood as a way to suppress magnetismand mimic the effects of quantum fluctuations ignored in DFT calculations. Withthese considerations, the resulting optical spectra reproduce the SDW gap and anumber of experimentally observed features related to the antiferromagneticorder. We find electronic contributions to excitations that so far have beenattributed to purely phononic modes. Also, an orbital resolved analysis of theoptical conductivity reveals significant contributions from all Fe 3d orbitals.Finally, we observe that there is an important renormalization of kineticenergy in these SDW metals, implying that the effects of correlations cannot beneglected.



Autor: Johannes Ferber, Yu-Zhong Zhang, Harald O. Jeschke, Roser Valenti

Fuente: https://arxiv.org/







Documentos relacionados