Fermi-Surface Shrinking and Interband Coupling in Iron-Based Pnictides

Recent measurements of the Fermi surface with de Haas–van Alphen oscillations in LaFePO showed a shrinking of the Fermi pockets with respect to first-principle calculations, suggesting an energy shift of the hole and electrons bands with respect to local-density approximations. We show that this shift is a natural consequence of the strong particle-hole asymmetry of electronic bands in pnictides, and that it provides an indirect experimental evidence of a dominant interband scattering in these systems.

Figure 1

Sketch of our band structure model (a) and of the corresponding Fermi surfaces (b). We also show the only nonzero interband couplings.

Figure 2

(a) Bands shift ${\chi }_{0,\alpha }$ as a function of the interband coupling $V$ for the parameter set taken from LDA calculations (Table , top). The horizontal dashed lines mark the average band shift as estimated in Refs. [14, 15]; (b) same as in panel (a) but considering LDA band structure renormalized by a factor 2 (Table , bottom).

Figure 3

Intensity map of the spectral function for the interacting hole bands (left panel) and the two degenerate electron bands (right panel), obtained by using LDA parameters renormalized by a factor 2 and $V=0.46\mathrm{eV}$. The dashed lines represent the noninteracting parabolic bands, and the horizontal solid line is the chemical potential. The ticks on the top mark the value of the Fermi vectors in the presence (solid yellow ticks) and in the absence (white dashed ticks) of interaction. Note the shrinking of the Fermi surfaces due to the coupling to the retarded bosonic mode.