https://doi.org/10.1140/epjst/e2010-01302-4
Regular Article
Electron interactions and charge ordering in CuO2 compounds
1 Walther Meissner Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
2 Central Research Institute of the Electric Power Industry, Komae, Tokyo 201-8511, Japan
3 Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
4 Department of Physics and Astronomy, University of British Columbia, Vancouver V6T 1Z4, Canada
5 Canadian Institute for Advanced Research, Toronto M5G 1Z8, Canada
a e-mail: bernhard.muschler@wmi.badw.de
b Present address: Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
Received:
14
July
2010
Revised:
12
August
2010
Published online:
11
October
2010
We present results of inelastic light scattering experiments on single-crystalline La2-xSrxCuO4 in the doping range 0.00 ≤ x = p ≤ 0.30 and Tl2Ba2CuO6+δ at p = 0.20 and p = 0.24. The main emphasis is placed on the response of electronic excitations in the antiferromagnetic phase, in the pseudogap range, in the superconducting state, and in the essentially normal metallic state at x ≥ 0.26, where no superconductivity could be observed. In most of the cases we compare B1g and B2g spectra which project out electronic properties close to (π, 0) and (π/2,π/2), respectively. In the channel of electron-hole excitations we find universal behavior in B2g symmetry as long as the material exhibits superconductivity at low temperature. In contrast, there is a strong doping dependence in B1g symmetry: (i) In the doping range 0.20 ≤ p ≤ 0.25 we observe rapid changes of shape and temperature dependence of the spectra. (ii) In La2-xSrxCuO4 new structures appear for x < 0.13 which are superposed on the electron-hole continuum. The temperature dependence as well as model calculations support an interpretation in terms of charge-ordering fluctuations. For x ≤ 0.05 the response from fluctuations disappears in B1g and appears in B2g symmetry in full agreement with the orientation change of stripes found by neutron scattering. While, with a grain of salt, the particle-hole continuum is universal for all cuprates the response from fluctuating charge order in the range 0.05 ≤ p < 0.16 is so far found only in La2-xSrxCuO4. We conclude that La2-xSrxCuO4 is close to static charge order and, for this reason, may have a suppressed Tc.
© EDP Sciences, Springer-Verlag, 2010