Heat capacity of superconducting La1.85Sr0.15CuO4

Abstract

The heat capacity has been obtained for a sample of ${\mathrm{La}}_{1.85}$ ${\mathrm{Sr}}_{0.15}$ ${\mathrm{CuO}}_4$ which is superconducting with a transition temperature $T_c$=31 K. Although the heat capacity is dominated by the lattice in the vicinity of $T_c$, it has nonetheless been possible to observe the superconducting transition, thus verifying that this is bulk superconductivity. A lower limit is established for the heat-capacity anomaly of ΔC/$T_c$=(20±5) mJ/mole $K^2$. Combined with estimates of the electronic heat capacity γ, this leads to 2≤ΔC/γ$T_c$≤10, compared with the Bardeen-Cooper-Schrieffer value of 1.43, which places this material well into the strong-coupling regime.