Orbital character and electron correlation effects on two- and three-dimensional Fermi surfaces in KFe2As2 revealed by angle-resolved photoemission spectroscopy

Abstract

We have investigated orbital character and electron correlation effects on Fermi surfaces in the hole-overdoped iron pnictide superconductor KFe 2 As 2 , which shows a low T c of ∼4 K, by angle-resolved photoemission spectroscopy. From the polarization-dependence of the ARPES spectra, we have determined the orbital character of each Fermi surface. Electron mass renormalization of each band is quantitatively consistent with de Haas-van Alphen results. The outer β and middle ζ Fermi surfaces show large renormalization factor of m * /m b ∼6-7, while the inner α Fermi surface has a smaller factor m * /m b ∼2. Middle hole Fermi surface ζ has strong three-dimensionality compared to other Fermi surfaces, indicating the d 3z2−r2 orbital character, which may be related to the "octet-line nodes" recently observed by laser ARPES. The observed orbital-dependent mass renormalization would give constraints on the pairing mechanism with line nodes of this system.

Fermi Surface of KFe2As2from Quantum Oscillations in Magnetostriction

“…Unfortunately, we did not collect data for Sample 2 at intermediate temperatures, making difficult an accurate estimation of the effective mass. The amplitudes of the FT peaks at 7.18 kT set a lower limit for m * /m e ∼ 16 for the β cylinder, in agreement with m * /m e = 16-19 recently obtained from dHvA and ARPES experiments [9,11,12].…”

“…The values of the effective mass extracted from our magnetostriction data λ(H), and from previously reported dHvA [9,12] and ARPES [11] experiments, are collected in Table I. The extracted high effective masses are consistent with the enhanced Sommerfeld coefficient present in this compound.…”

“…1(d)], with an amplitude larger than that of the second harmonic of α Γ,Z . A peak associated with the β cylinder is expected to appear at this frequency, following the estimation of the FS cross-sectional area given by ARPES [11]. Given that the amplitude of harmonics decreases exponentially with harmonic number, we can assign our 7.18 kT peak to orbits in the β cylinder [9,12].…”

“…Table I. Effective masses m * determined from dHvA [9,12], ARPES [11] and our magnetostriction measurements (λ). The frequencies F and Fermi velocities v F calculated from our data are given in the last two columns (values marked with * are taken from Ref.…”

“…As the chemical potential changes with increasing K concentration, the corner cylinders transform into hole Fermi sheets [8]. The FS of KFe 2 As 2 is formed by quasi-two-dimensional hole cylinders aligned with the k z -axis: three (α, ζ and β) centered at the Γ-point, and hole cylinders near the X-point [6,[9][10][11][12]. Additionally, small three-dimensional hole pockets were predicted theoretically to exist at the Zpoint [9,10].…”