Effect of flux pinning on the Nernst and Ettingshausen effects in high-T-csuperconductors

Theoretical expressions for the Nernst and Ettingshausen coefficients in hi gh-T-c cuprate superconductors are derived by taking account of the effects of flux pinning. It is shown that these coefficients are essentially subje cted by the flux pinning characteristics of the sample even above the glass liquid transition temperature, T-GL, where the observed values of these co efficients become dominant. While the existing observed data are not suffic ient for carrying out the quantitative comparison with the present theory b ecause of the lack of the description on the detailed pinning characteristi cs of the observed sample, a preliminary comparison with the existing obser ved data showed a semi-quantitative agreement under the choice of reasonabl e values for the pinning characteristics of the sample, except in the vicin ity of the critical temperature where the fluctuating appearance of superco nductivity cannot be neglected. Then the present theory can be a target of the quantitative comparison with future detailed measurements. (C) 1999 Els evier Science B.V. All rights reserved.