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Reply to Comment on arXiv:1012.1484v1 Structural origin of apparent Fermi surface pockets in angle-resolved photoemission of Bi_2Sr_{2-x}La_xCuO_{6+delta} by King et al.

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 Added by Philip King
 Publication date 2011
  fields Physics
and research's language is English




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Reply to comment by Zhou et al. (arXiv:1012.3602) on arXiv:1012.1484 / Phys. Rev. Lett. 106, 127005 (2011).

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We observe apparent hole pockets in the Fermi surfaces of single-layer Bi-based cuprate superconductors from angle-resolved photoemission (ARPES). From detailed low-energy electron diffraction measurements and an analysis of the ARPES polarization-dependence, we show that these pockets are not intrinsic, but arise from multiple overlapping superstructure replicas of the main and shadow bands. We further demonstrate that the hole pockets reported recently from ARPES [Meng et al, Nature 462, 335 (2009)] have a similar structural origin, and are inconsistent with an intrinsic hole pocket associated with the electronic structure of a doped CuO$_2$ plane. The nature of the Fermi surface topology in the enigmatic pseudogap phase therefore remains an open question.
A first Fermi surface map of a single-layer high-Tc superconductor is presented. The experiments were carried out on optimally doped Bi_2Sr_(2-x)La_xCuO_(6+delta)(x=0.40) with synchrotron radiation which allow to discuss in detail the strong polarisation dependence of the emissions near the Fermi edge. For the cuprates only little is known about the impact of the electron-photon matrix element determining the photoelectron intensity. For the example of the model layered superconductor Bi_2Sr_(2-x)La_xCuO_(6+delta)it will be demonstrated that the polarization geometry has significant influence on the energy distribution curves at EF and consequently also for the determination of the topology and character of the Fermi surface (FS) by angle-resolved photoemission. For further clarification also a FS map of the n=2 material Bi-2212 has been measured applying a different polarisation geometry as previously used by Saini et al.. In the context of the current debate on the character of the Fermi surface of Bi-cuprates our results confirm a hole-like Fermi surface for n=1 as well as n=2 material, what might be the universal FS for high-Tc superconductors.
Here we apply high resolution angle-resolved photoemission spectroscopy (ARPES) using a wide excitation energy range to probe the electronic structure and the Fermi surface topology of the Ba1-xKxFe2As2 (Tc = 32 K) superconductor. We find significant deviations in the low energy band structure from that predicted in calculations. A set of Fermi surface sheets with unexpected topology is detected at the Brillouin zone boundary. At the X-symmetry point the Fermi surface is formed by a shallow electron-like pocket surrounded by four hole-like pockets elongated in G-X and G-Y directions.
Recently observed splitting in angular resolved photoemission spectroscopy (ARPES) on $chem{Bi_2Sr_{2-x}La_xCuO_{6+delta}}$ high--temperature superconductor (Janowitz C. {it et al.}, {it Europhys. Lett.}, {bf 60} (2002) 615) is interpreted within the phenomenological Luttinger--liquid framework, in which both the non--Fermi liquid scaling exponent of the spectral function and the spin--charge separation are introduced. The anomalous Green function with adjustable parameters fits very well to the Fermi edge and the low--energy part of ARPES along the $Gamma-M$ line in the Brillouin zone. In contrast to one--dimensional models with Luttinger--liquid behavior we find that both the anomalous scaling $alpha$ and the parameter $delta$ describing the spin--charge separation are momentum dependent. The higher--energy part of the spectra is not accounted for by this simple Luttinger--liquid form of the Green function. In this energy regime additional scattering processes are plausible to produce the experimentally observed wide incoherent background, which diminishes as the inverse of the energy.
In a comment on arXiv:1006.5070v1, Drechsler et al. present new band-structure calculations suggesting that the frustrated ferromagnetic spin-1/2 chain LiCuVO4 should be described by a strong rather than weak ferromagnetic nearest-neighbor interaction, in contradiction with their previous calculations. In our reply, we show that their new results are at odds with the observed magnetic structure, that their analysis of the static susceptibility neglects important contributions, and that their criticism of the spin-wave analysis of the bound-state dispersion is unfounded. We further show that their new exact diagonalization results reinforce our conclusion on the existence of a four-spinon continuum in LiCuVO4, see Enderle et al., Phys. Rev. Lett. 104 (2010) 237207.
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