Soft x-ray absorption and high-resolution powder x-ray diffraction study of superconducting Ca La1−Ba1.75−La0.25+Cu3O system

Abstract

Abstract. We have studied the electronic structure of unoccupied states measured by O K-edge and Cu L-edge x-ray absorption spectroscopy (XAS), combined with crystal structure studied by

Correlation of the superconducting critical temperature with spin and orbital excitations in(CaxLa1−x)(Ba1.75−Ellis1, Huang2, Olalde-Velasco3 et al. 2015Phys. Rev. B311191View full textAdd to dashboardCite

“…The second peak B is at the same energy for all samples. It corresponds to the same absorption process as A, but in the presence of a ligand hole, namely, Cu 3d 9L → Cu 2p3d 10L [22,50]. It is clear that peak B becomes less and less intense as the doping decreases, but is roughly the same between x = 0.1 and x = 0.4 for identical nominal dopings.…”

“…Referring to Fig. 11, the data were normalized so as to have the same maxima of peak A for all samples, which comes from the Cu 3d 9 → Cu 2p3d 10 transition [22,50]. The low-energy edges of the A peaks of all samples match perfectly, with the exception of x = 0.4 UD, whose A peak is shifted to slightly lower energy.…”

“…The number of holes can be determined from the relative B peak intensity [22,54]. The spectra were fitted to three Lorentzians, as shown in Fig.…”

“…Therefore, x tunes both J (through a and θ ) and orbital splitting (through d A ) over the whole phase diagram. Moreover, disorder in CLBLCO was found to be x independent based on the linewidths measured by techniques ranging from high-resolution powder x-ray diffraction [22], Cu, Ca, and O nuclear magnetic resonance [23][24][25][26], phonon [27], and angle-resolved photoemission spectroscopy (ARPES) [28]. Intriguingly, both J , as measured in undoped CLBLCO samples, and T [29], which plots the Néel (T N ), spin-glass (T g ), and superconducting (T c ) transition temperatures as a function of the stoichiometric oxygen amount y for various families (x).…”

Relevance of magnetism to cuprate superconductivity: Lanthanides versus charge-compensated cuprates

“…In contrast, T max c appears to show an anomalous suppression which grows with decreasing x, thereby effectively reversing its correlation with J. The reasons for such a suppression are not apparent and, for example, NMR studies suggest it is not associated with disorder scattering [16][17][18]. These are interesting model systems that deserve more study if systematic behavior is to be elucidated.…”