Fermi Surface of KFe₂As₂from Quantum Oscillations in Magnetostriction

Abstract

We present a study of the Fermi surface of KFe 2 As 2 single crystals. Quantum oscillations were observed in magnetostriction measured down to 50 mK and in magnetic fields µ 0 H up to 14 T. For H c, the calculated effective masses are in agreement with recent de Haas-van Alphen and ARPES experiments, showing enhanced values with respect to the ones obtained from previous band calculations. For H a, we observed a small orbit at a cyclotron frequency of 64 T, characterized by an effective mass of ∼ 0.8 m e , supporting the presence of a three-dimensional pocket at the Z-point.

Electronic structure and de Haas–van Alphen frequencies in KFe2As2within LDA+DMFT

“…We would like to note that quantum oscillation experiments [44] and ARPES [13,16] reported the existence of a fourth very small pocket centred at the Z point which was not seen in our calculations for the most recent structure. This fourth pocket is however present in the DFT calculation when using the structure from Rosza and Schuster [26], but we found it to vanish when adding correlations in LDA+DMFT, depending on the double-counting (see appendix).…”

Universal V-shaped temperature-pressure phase diagram in the iron-based superconductorsKFe2As2,RbFe2As2, andTafti1, Ouellet2, Juneau-Fecteau3 et al. 2015Phys. Rev. B

“…There is also one small 3D hole pocket at the Z point of the Brillouin zone. 12 The pairing symmetry of KFe 2 As 2 at ambient pressure is the subject of ongoing debate. Laser ARPES experiments suggest a s ± state with eight line nodes on the ξ band and no nodes on the α and β bands.…”

Van Hove singularities, chemical pressure and phonons: an angle-resolved photoemission study of KFe$_2$As$_2$ and CsFe$_2$As$_2$

“…Although this would not affect much the weakly k z -dispersive bands, the effect should be sizable for the d z 2 band. In particular, we suspect that such k z averaging effect should reduce the apparent dispersion along k z , and we cannot exclude the possibility that this band crosses E F at the Z point, forming a three-dimensional FS pocket, as proposed by quantum oscillation experiments [24]. In any case, the d z 2 band is certainly affected by the chemical pressure, as illustrated by the EDCs at the Γ and Z points shown in Fig.…”

“…2 a series of Fermi surface (FS) mappings recorded on KFe 2 As 2 and CsFe 2 As 2 in the k z = 0 and k z = π planes, under both σ and π configurations of polarization. Although the FSs of KFe 2 As 2 and CsFe 2 As 2 have already been reported and described in previous ARPES [9,[28][29][30][31] and quantum oscillation studies [24,[32][33][34], some comments need to be made. The FS patterns recorded around the M (1, 0, k z = 0) and A (1, 0, k z = π) points are practically equivalent, indicating that there is not much k z dispersion along M-A.…”

“…In Section III, we compare ARPES data recorded on KFe 2 As 2 and CsFe 2 As 2 , with the chemical substitution of K by Cs acting similarly to the application of a negative pressure [21,22]. We show that the 3d z 2 states responsible for the small threedimensional hole pocket reported in quantum oscillation measurements [24] are less k z -dispersive in CsFe 2 As 2 than in KFe 2 As 2 , but that they are located closer to E F . Interestingly, the van Hove singularity located midway between the Γ and M points, directly on the nodal line of the s ± function, and identified previously as candidate for the nodal behavior in KFe 2 As 2 [25], also moves closer to E F with decreasing chemical pressure.…”