Complete Fermi Surface inBaFe2As2Observed via Shubnikov–de Haas Oscillation Measurements on Detwinned Single Crystals

Abstract

We show that the Fermi surface (FS) in the antiferromagnetic phase of BaFe(2)As(2) is composed of one hole and two electron pockets, all of which are three dimensional and closed, in sharp contrast to the FS observed by angle-resolved photoemission spectroscopy. Considerations on the carrier compensation and Sommerfeld coefficient rule out existence of unobserved FS pockets of significant sizes. A standard band structure calculation reasonably accounts for the observed FS, despite the overestimated ordered moment. The mass enhancement, the ratio of the effective mass to the band mass, is 2-3.

Quantum oscillations inEuFe2As2single crystals

“…Our results for Ba122 are in good agreement with previous reports [18][19][20] and the unprecedented observation of QO in Eu122 indicates that the Indium flux technique yields high quality single crystals. Subtle changes in the fermiology of Eu122, such as band splitting and a significant increase of isotropy and threedimensionality of the bands, are clearly noticed when comparing the data with those of Ba122.…”

“…The corresponding frequencies are listed in Table I by adopting an identical labeling of the branches as in Ref. 20 . In particular, we also attribute the β branch reported in Ref.…”

“…However, we will show that a fairly good agreement with the experiments could be obtained by performing band structure calculations for both Ba122 and Eu122 compounds using the LDA+U approach, as detailed in Section II. As usually performed in these materials [17][18][19][20] , in order to improve the agreement between the calculated and the measured frequencies, we have shifted the energies of the α, δ, and γ bands of Ba122 by + 48 meV, -54 meV, and +35 meV, respectively, and those of Eu122 by + 41 meV, -54 meV, and -30 meV, respectively. The calculated effective masses, m * DF T , also display agreement with the experimental data, as shown in Table I.…”

“…In particular, low temperature QO experiments have been reported on several members of the 122 family AFe 2 As 2 (A = Ba, Ca, Sr) providing both high resolution of the FS in momentum space and important information on the effective masses [18][19][20][21] . In particular, three low frequency Fourier peaks have been observed for BaFe 2 As 2 at F δ = 500 T, F α = 440 T, and F γ = 90 T, each of them occupying about 2% of the nonmagnetic BZ.…”

Origin of the Resistivity Anisotropy in the Nematic Phase of FeSe

“…The fact that the resistivity anisotropy is much larger than what is expected from the small lattice distortion led to the proposal that the tetragonal-to-orthorhombic transition in the iron pnictides is driven not by phonons, but by an electronic nematic phase. Subsequent experiments revealed an intricate dependence of the resistivity anisotropy on doping (a sign change between electron-and hole-doped materials [2-6]), and disorder [7,8], sparking hot debates about its microscopic origins (see Refs. [9 and 10] for reviews).…”