Pseudogap-related charge dynamics in layered-nickelate R2-xSrxNiO4 (x sim 1)

Abstract

Charge dynamics and its critical behavior are investigated near the metal-insulator transition of layered-nickelate R2-xSrxNiO4 (R=Nd, Eu). The polarized x-ray absorption spectroscopy experiment clearly shows the multi-orbital nature which enables the x2-y2-orbital-based checkerboard-type charge ordering or correlation to persist up to the critical doping region (x sim 1). In the barely metallic region proximate to the charge-ordered insulating phase, the nominal carrier density estimated from the Hall coefficient markedly decreases in accord with development of the pseudogap structure in the optical conductivity spectrum, while the effective mass is least enhanced. The present findings combined with the results of recent angle-resolved photoemission spectroscopy show that the pseudogap in the metal-insulator critical state evolves due to the checkerboard-type charge correlation to extinguish the coherent-motion carriers in a characteristic momentum (k)-dependent manner with lowering temperature.

7 pages, 6 figures. Accepted in Physical Review B

References in corpus (4)

• Pseudogap of metallic layered nickelate R2-xSrxNiO4 (R=Nd, Eu) crystals measured using angle-resolved photoemission spectroscopy
• Unidirectional Diagonal Order and 3D Stacking of Charge Stripes in Orthorhombic Pr1.67Sr0.33NiO4 and Nd1.67Sr0.33NiO4
• Structural changes at the semiconductor-insulator phase transition in the single layered La0.5Sr1.5MnO4 perovskite
• Orbital characters of three-dimensional Fermi surfaces in Eu2-xSrxNiO4 as probed by soft-x-ray angle-resolved photoemission spectroscopy

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• Structural disorder and magnetic correlations driven by oxygen doping in Nd2NiO4+d (d ~ 0.11)
• Localized character of charge excitations for La${}_{2-x}$Sr${}_x$NiO${}_{4+\delta }$ revealed by oxygen $K$-edge resonant inelastic X-ray scattering
• Magnetic excitations in Nd${}_{n+1}$Ni${}_n$O${}_{3n+1}$ Ruddlesden-Popper nickelates observed via resonant inelastic x-ray scattering
• Charge disproportionation and nano phase separation in $R$SrNiO${}_4$