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Electronic structures of high‐ T c superconductors LnBa 2 Cu 3 O 7 (Ln Pr, Nd, Gd, Dy)
Author(s) -
Li Ming
Publication year - 1993
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560480104
Subject(s) - superconductivity , fermi level , fermi surface , crystallography , superconducting transition temperature , electronic structure , condensed matter physics , materials science , chemistry , physics , electron , quantum mechanics
In the present paper, the electronic energy‐band structures of the LnBa 2 Cu 3 O 7 (Ln = Pr, Nd, Gd, and Dy) were investigated employing the EHMO approach based on the tight‐binding method. The results show that the substitution of Nd, Gd, and Dy for Y in YBa 2 Cu 3 O 7 complicates the shape of the Fermi surface and results in an increase in the number of energy bands crossing the Fermi level, Ef . Compared with those of YBa 2 Cu 3 O 7 , the electronic densities of states at Ef, N(Ef) , for NdBa 2 Cu 3 O 7 , GdBa 2 Cu 3 O 7 , and DyBa 2 Cu 3 O 7 increase greatly, whereas those of PrBa 2 Cu 3 O 7 are very small. The results given by the present calculations explain why the substitution of Nd, Gd, and Dy for Y in YBa 2 Cu 3 O 7 can still maintain the high transition temperature T c , while PrBa 2 Cu 3 O 7 is a semiconductor rather than a superconductor. © 1993 John Wiley & Sons, Inc.