大型放射光施設 SPring-8

Speaker : Dr. Jonathan Pelliciari

Language : English

Affiliation : Massachusetts Institute of Technology

Title : Resonant Inelastic X-ray Scattering on Iron Pnictides

Abstract :
　I will describe Resonant Inelastic X-Ray Scattering (RIXS) and Kbeta X-ray emission spectroscopy experiments on Fe pnictides. I will present RIXS study of parent and doped NaFe_1-xCo_xAs spanning optimal and overdoped regimes [1]. Spectral shape decomposition reveals the persistence of broad dispersive magnetic excitations for all doping levels. In contrast to previous RIXS experiments on hole-doped BaFe₂As₂ compounds [2], the energy of such modes is not strongly affected by doping and the magnetic weight per iron atom of magnons / paramagnons remains sizable. We argue that cobalt-doping is mainly tuning the electronic correlations.
　I will further discuss the work carried out on the BaFe₂(As_1-xP_x)₂ series where SC appears upon isovalent doping [3]. I present a combined RIXS and XES study of parent and doped BaFe₂(As_1-xP_x)₂ spanning a large portion of the phase diagram. RIXS measurements reveal the persistence of broad dispersive magnetic excitations for all doping levels. Remarkably, the energy of such modes is strongly hardened by doping contrasting with the case of hole-doped BaFe₂As₂ [2]. Moreover their spectral weight is conserved along the phase diagram. XES experiments show a gradual quenching of the local magnetic moment, intriguing if compared to the behavior of spin correlations. Employing intermediate coupling calculations (DFT-GW), we link the unconventional evolution of magnetism to the shift from 2- to 3-dimensional electronic structure of the system, hand in hand with the warping of the Fermi surface. This speaks for a picture where unconventional SC emerges from a balance of local and correlated magnetism, further demonstrating that magnetism is not detrimental for SC.

[1] J. Pelliciari et al Phy Rev B 93, 134515 (2016)
[2] K. J. Zhou et al, Nat. Comm., 4, 1470 (2013)
[3] D. C. Johnston, Advances in Physics Vol. 59, No. 6, 803 (2010)

担当者：量子科学技術研究開発機構（QST） 石井賢司
e-mail: kenjispring8.or.jp／PHS: 3128
JASRI　櫻井吉晴
e-mail：sakuraispring8.or.jp／PHS：3803