Relationship between a charge-transfer energy and the configuration of a 2D Wigner lattice in high-T c superconductors

1996 ◽  
Vol 46 (S2) ◽  
pp. 927-928 ◽  
Author(s):  
S. Kuwata ◽  
W. Kinase
Keyword(s):  
Charge Transfer ◽  
Transfer Energy ◽  
Charge Transfer Energy ◽  
A Charge ◽  
Wigner Lattice

ELECTRONIC CHANGES RELATED TO THE METAL-TO-INSULATOR PHASE TRANSITION IN RNiO3

2002 ◽  
Vol 09 (02) ◽  
pp. 1121-1125 ◽  
Author(s):  
CÍNTHIA PIAMONTEZE ◽  
HÉLIO C. N. TOLENTINO ◽  
FLÁVIO C. VICENTIN ◽  
ALINE Y. RAMOS ◽  
NESTOR E. MASSA ◽  
...  
Keyword(s):  
Phase Transition ◽  
Rare Earth ◽  
Charge Transfer ◽  
Transition Temperature ◽  
Antiferromagnetic Order ◽  
Transfer Energy ◽  
Multiplet Splitting ◽  
Charge Transfer Energy ◽  
A Charge ◽  
Insulating Phase

Rare earth nickel oxide perovskites (R NiO 3, R=rare earth) have, except for LaNiO 3, a metal–insulator (MI) phase transition as temperature decreases. The transition temperature (T MI ) increases as the R-ion becomes smaller. They present also, at low temperatures, a complex antiferromagnetic order. For lighter R-ions (e.g. Pr and Nd), the antiferromagnetic transition temperature (T N ) is close to T MI , while for heavier R-ions (e.g. Eu, Sm), T MI and T N are very far apart, suggesting that the magnetic and electronic behaviors are not directly coupled. Although R NiO 3 perovskites are placed in the boundary of the Mott–Hubbard and charge transfer regimes, there are several evidences pointing to a charge transfer gap, mainly controlled by ligand-to-metal charge transfer energy, and thus strongly dependent on hybridization. Ni L-edge absorption spectroscopy (transition 2p → 3d) gives direct information on the density of Ni 3d empty states, and in particular on the multiplet splitting and hybridization between Ni 3d and O 2p bands. Here we present Ni L3 and L2 absorption spectra measured for NdNiO 3 and EuNiO 3 (T MI = 200 and 480 K). At room temperature, dramatic differences are observed between EuNiO 3 (insulating) and NdNiO 3 (metallic). The normalized spectra give evidence for a higher density of 3d unoccupied states and a larger multiplet splitting in EuNiO 3. Both effects might be correlated to a decrease in hybridization. The same behavior is observed for NdNiO 3 as it is cooled down to the insulating phase (T < 200 K), revealing that in these compounds the opening of the gap is directly related to the degree of hybridization.

F−-Eu3+ charge transfer energy and local crystal environment in Eu3+ doped calcium fluoride

2017 ◽  
Vol 43 (16) ◽  
pp. 13089-13093 ◽  
Author(s):  
Yu Pan ◽  
Wenjun Wang ◽  
Liqun Zhou ◽  
Haibing Xu ◽  
Qinghua Xia ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Calcium Fluoride ◽  
Transfer Energy ◽  
Charge Transfer Energy

Origin of the Band Gap in the Negative Charge-Transfer-Energy Compound NaCuO2

1993 ◽  
Vol 70 (10) ◽  
pp. 1565-1565 ◽  
Author(s):  
T. Mizokawa ◽  
H. Namatame ◽  
A. Fujimori ◽  
K. Akeyama ◽  
H. Kondoh ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Band Gap ◽  
Negative Charge ◽  
Transfer Energy ◽  
Charge Transfer Energy
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