Dependences of the chemical potential shift and superconducting transition temperature on the hole concentration in La_(2-x)Sr_xCuO_4 and Bi_2Sr_2Ca_(1- x)Y_xCu_2O_(8+#delta#)

摘要

Dependences of the superconducting transitiontemperature (T_c) on the hole concentration (n_h) in La_(2-x)Sr_xCuO_4 and Bi_2Sr_2Ca_(1-x)Y_xCu_2O_(8+#delta#)have been calculated using the interband model. The phase spacefor pair-transfer scattering between the overlapping bands isgoverned by the position of the chemical potential. Downwardshifts (#DELTA##MU#) of the electron chemical potential(#mu#) with the n_h have been found. The slope is partialderiv#mu#/ partial deriv n_h ? 8 eV/hole in under-dopedBi_2Sr_2Ca_(1-x)Y_xCu_2O_(8+#delta#) and it becomessmaller in optimally-doped and over-doped samples (approx 1.2eV/hole). In La_(2-x)Sr_xCuO_4 partial deriv#mu#/ partialderiv n_h is equal of 1.25 eV/hole in over-doped samples andapprox 0.4 eV/hole in under-doped samples at T=80K. Thepseudogap leads to the suppression of #DELTA##mu#(n_h) upto n_h ?0.17 holes per CuO_2 plane at T =80 K. The shift of thechemical potential #mu# leads to the curve T_c(n_h) with amaximum. The dependences #DELTA##mu#(n_h) and T_c(n_h)for the systems considered agree with the experimental data.