Specific Heat of YBa2Cu3O7−−δ and (La 2 − x Sr x )CuO4: Evidence for d-Wave Pairing

New low-temperature specific-heat data for YBa 2 Cu 3 O 7−δ , 0≤δ≤0.2, and (La 1.85 Sr 0.15 )CuO 4 in magnetic fields ( H ) to 9 T are reported. They show features predicted for the lines of nodes in the energy gap that are expected for d -wave pairing; for H =0, a T 2 term; for H ≠0 an H 1/2 T term with a crossover to a more complicated T dependence at higher T and lower H . The results are compared with recent measurements in other laboratories.