Fermi surface in KFe2As2determined via de Haas–van Alphen oscillation measurements

Abstract

We have completely determined the Fermi surface in KFe2As2 via de Haas-van Alphen (dHvA) measurements. Fundamental frequencies ǫ, α, ζ, and β are observed in KFe2As2. The first one is attributed to a hole cylinder near the X point of the Brillouin zone, while the others to hole cylinders at the Γ point. We also observe magnetic breakdown frequencies between α and ζ and suggest a plausible explanation for them. The experimental frequencies show deviations from frequencies predicted by band structure calculations. Large effective masses up to 19 me for B c have been found, me being the free electron mass. The carrier number and Sommerfeld coefficient of the specific heat are estimated to be 1.01 -1.03 holes per formula unit and 82 -94 mJmol −1 K −2 , respectively, which are consistent with the chemical stoichiometry and a direct measure of 93 mJmol −1 K −2 [H. Fukazawa et al., J. Phys. Soc. Jpn. 80SA, SA118 (2011)]. The Sommerfeld coefficient is about 9 times enhanced over a band value, suggesting the importance of low-energy spin and/or orbital fluctuations, and places KFe2As2 among strongly correlated metals. We have also performed dHvA measurements on Ba0.07K0.93Fe2As2 and have observed the α and β frequencies.

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

“…The orbital character of each FS is determined by the polarization dependence of the ARPES intensity. The value of the electron mass renormalization for each band indicates orbital-dependent correlation effects and is consistent with the dHvA result [20,21] and the DMFT calculation [25]. Particularly, the β and ζ FS show large mass enhancement of m * /m b ∼ 6-7.…”

“…So far, strong mass renormalization has been observed from the electronic specific heat coefficient γ as large as ∼70-100 mJ/K 2 mol [12,19]. Also, both the ARPES [18] and dHvA studies [20,21] have indicated the enhancement of the electron masses compared to those predicted by the band-structure calculation.…”

Magnetic interactions in iron superconductors: A review

“…Orbital differentiation increases with hole-doping [40,119] and could be behind the sensitivity to structural details [112,116]. Among the experimental signatures of orbital differentiation are: (i) ARPES and quantum oscillations experiments have reported important differences in orbital correlations in KFe 2 As 2 [197,198]; (ii) The deviations from LDA predictions of the Fermi surface of LiFeAs, LaFePO and LiFeP observed experimentally have been adscribed to the orbital dependent mass enhancement and the interaction dependent orbital occupancy [212,213]; (iii) ARPES experiments in 122 chalcogenides have been interpreted in terms of a temperature induced OSMT [41,189].…”

Fermi Surface of KFe2As2from Quantum Oscillations in Magnetostriction

“…For H c, quantum oscillations (QOs) in the magnetostriction λ a (L a) were observed above H c c2 = 1.5 T up to 14 T. , which correspond to the low and high components of the α and cylinders previously determined from de Haas-van Alphen (dHvA) measurements [9,12]. Additional peaks are observed at 2.55, 2.61 and 2.66 kT, which we could not identify with the cyclotron orbits of the ζ and β cylinders, not with harmonics of the peaks.…”

“…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.…”