TEMPERATURE DEPENDENCES OF THE RESISTIVITY AND HALL-COEFFICIENT OF UNTWINNED SINGLE-CRYSTAL YBA2CU3O7-DELTA AT CONSTANT VOLUME

The previously published constant-pressure temperature dependences of the resistivity eigenvalues and Hall coefficient of untwinned single-crystal YBa2Cu3O7-delta are used, together with the coefficient of expansion and the compressibility, to calculate the constant-volume temperature dependences of these transport coefficients, since the constant-volume values are the quantities that have been predicted by theories of high-temperature superconductivity. It is found that the in-plane resistivity eigenvalues at constant volume are slightly lower and more nearly linear in the temperature than at constant pressure. The c-axis resistivity at constant volume is also slightly lower than at constant pressure, and approximately as linear. G(H), the reciprocal of the Hall coefficient R(H), at constant volume is slightly higher and just as nearly linear in the temperature as at constant pressure. The cotangent of the Hall angle, as a function of T2, is essentially the same at constant pressure as at constant volume, and remains linear in T2.