| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Steeneken, P. G., et al.
(författare)
-
Crossing the gap from p- to n-type doping : Nature of the states near the chemical potential in La2-xSrxCuO4 and Nd2-xCexCuO4-delta
- 2003
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 90:24
-
Tidskriftsartikel (refereegranskat)abstract
- We report on an x-ray absorption and resonant photoemission study on single crystals of the high-T-c cuprates La2-xSrxCuO4 and Nd2-xCexCuO4-delta. Using an intrinsic energy reference, we find that the chemical potential of La2-xSrxCuO4 lies near the top of the La2CuO4 valence band whereas in Nd2-xCexCuO4-delta it is situated near the bottom of the Nd2CuO4 conduction band. The data clearly establish that the introduction of Ce in Nd2CuO4 results in electrons being doped into the CuO2 planes. We infer that the states closest to the chemical potential have a Cu 3d(10) singlet origin in Nd2-xCexCuO4-delta and a 3d(9) (L) under bar singlet origin in La2-xSrxCuO4.
|
|
| 5. |
|
|
| 6. |
- Tjernberg, Oscar, et al.
(författare)
-
Electrons, holes, and spin in Nd2-xCexCuO4-delta
- 2003
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:10
-
Tidskriftsartikel (refereegranskat)abstract
- The spin nature of the states at the top of the valence band in Nd2CuO4 and Nd1.85Ce0.15CuO4-delta has been investigated with spin polarized resonant photoemission. A clear Zhang-Rice singlet state is observed at the top of the valence band in the undoped compound showing that the parent compound of this electron doped superconductor is similar to the parent compounds of hole doped cuprate superconductors. Upon doping, the stability of the singlet is destroyed and the optimum doped compound Nd1.85Ce0.15CuO4-delta does not display any well-separated singlet state. These results indicate that hole contribution to the superconductivity in this system is not important in contrast to what has previously been suggested on the bases of transport measurements.
|
|
| 7. |
- Brookes, N. B., et al.
(författare)
-
Detection of Zhang-Rice singlets using spin-polarized photoemission
- 2001
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 8723:23
-
Tidskriftsartikel (refereegranskat)abstract
- From a spin-resolved photoemission study on the Bi2Sr2CaCu2O8+delta superconductor, we show experimentally that the first ionization state is of nearly pure singlet character. This is true both above and below the superconducting transition and in the presence of doping and band formation. This provides direct support for the existence and stability of Zhang-Rice singlets in high-temperature superconductors, justifying the ansatz of single-band models. Moreover, we establish this technique as an important probe for a wide range of cuprates and strongly correlated materials.
|
|
| 8. |
- Ghiringhelli, G., et al.
(författare)
-
Probing the singlet character of the two-hole states in cuprate superconductors
- 2002
-
Ingår i: Physica. B, Condensed matter. - 0921-4526 .- 1873-2135. ; 312, s. 34-35
-
Tidskriftsartikel (refereegranskat)abstract
- Using spin-resolved resonant photoemission we have probed the singlet vs. triplet character of the two-hole state in the layered cuprates Bi2Sr2CaCu2O8+delta La2-xSrxCuO4 and Sr2CuO2Cl2. The combination of the photon circular polarization with the photoelectron spin detection gives access to the character of the photoemission final states, which correspond to the two-hole configurations localized at a (CuO4) site. In particular, the lowest energy state is found to have a very high singlet character in all the measured compounds. This can be considered as a strong indication of the existence and stability of the so-called Zhang-Rice singlets in the layered cuprates.
|
|
