Distinct oxygen hole doping in different layers ofSr2CuO4−δ/La2CuO4superlattices

Abstract

X-ray absorption in Sr2CuO 4−δ −La2CuO4 (SCO-LCO) superlattices shows a variable occupation with doping of a hole state different from holes doped for x x optimal in bulk La2−xSrxCuO4 and suggests that this hole state is on apical oxygen atoms and polarized in the a − b plane. Considering the surface reflectivity gives a good qualitative description of the line shapes of resonant soft X-ray scattering. The interference between superlattice and surface reflections was used to distinguish between scatterers in the SCO and the LCO layers, with the two hole states maximized in different layers of the superlattice.

Design and Differentiation of Quantum States at Subnanometer Scale in La2CuO4−Sr2CuO4−δ Superlattices

“…The first peak, ( i ) the HP at ∼529 eV (blue), is situated at lower binding energies compared to ( ii ) the UHB peak at ∼530 eV (red), and ( iii ) a shoulder of the main edge onset at 533.0 eV (turquoise). The results of this analysis are visually compelling and illustrate the efficiency of spectral-weight transfer from the UHB to the HP, which is located at lower binding energies. ,, In subsequent analyses, we aim to further dissect the interfacial area and examine the evolution of holes, Sr content, and oxygen-vacancy formation at the atomic scale.…”

“…In our work, we will address this emerging O-K edge prepeak as hole peak (HP). Chemical doping, such as Sr doping in LCO, shifts spectral weight from the upper Hubbard band (UHB) to the HP, thereby introducing holes into the system. − Polarization-dependent XAS provides information on orbital occupation through high energy resolution, ,, but with limited spatial resolution, which is inevitable for characterizing innovative applications like Josephson junctions . EELS bridges this gap, offering atomic-scale characterization of orbital occupation, and the ability to quantify cations and anions, and their physical properties as a function of position by probing different phases.…”

Different doping from apical and planar oxygen vacancies in Ba$_{2}$CuO$_{4-δ}$ and La$_{2}$CuO$_{4-δ}$

“…2 for the apical but not for planar O vacancies would be a key signature to look for with XPS. Notably, recent O K-edge x-ray absorption (XAS) experiments on SCO/LCO superlattices [23] have shown that the reduction of the second hole peak in the unoccupied DOS of SCO provides a signature of apical oxygen vacancies in SCO. In fact, earlier XAS measurements on overdoped LSCO [24] and electron energy-loss spectroscopy on SCO [25] have determined that such peaks belong to the apical oxygen unoccupied partial DOS.…”

Different doping from apical and planar oxygen vacancies in Ba2CuO4−δand La2Jarlborg1, Barbiellini2, Markiewicz3 et al. 2012Phys. Rev. B160190View full textAdd to dashboardCite

“…2 for the apical but not for planar O vacancies would be a key signature to look for with XPS. Notably, recent O K-edge x-ray absorption (XAS) experiments on SCO/LCO superlattices 23 have shown that the reduction of the second hole peak in the unoccupied DOS of SCO provides a signature of apical oxygen vacancies in SCO. In fact, earlier XAS measurements on overdoped LSCO 24 and electron energy-loss spectroscopy on SCO 25 have determined that such peaks belong to the apical oxygen unoccupied partial DOS.…”