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Carbon Doping in MgB_2 : Role of Boron and Carbon p_x(y) Bands

By Prabhakar P. Singh

Abstract

We have studied the changes in the electronic structure and the superconducting transition temperature T_c of Mg(B_{1-x}C_{x})_{2} alloys as a function of x with 0\leq x\leq 0.3. Our density-functional-based approach uses coherent-potential approximation to describe the effects of disorder, Gaspari-Gyorffy formalism to estimate the electron-phonon matrix elements and Allen-Dynes equation to calculate T_c in these alloys. We find that the changes in the electronic structure of Mg(B_{1-x}C_{x})_{2} alloys, especially near the Fermi energy E_F, come mainly from the outward movement of E_F with increasing x, and the effects of disorder in the B plane are small. In particular, our results show a sharp decline in both B and C p_{x(y)} states for 0.2\leq x\leq 0.3. Our calculated variation in T_{c} of Mg(B_{1-x}C_{x})_{2} alloys is in qualitative agreement with the experiments.Comment: 9 pages, 5 figure

Topics: Condensed Matter - Superconductivity, Condensed Matter - Materials Science
Publisher: 'Elsevier BV'
Year: 2003
DOI identifier: 10.1016/S0038-1098(03)00426-5
OAI identifier: oai:arXiv.org:cond-mat/0304436

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