Absence of specific-heat anomaly at the superconducting transition in La1.8Ba0.2CuO4−y

Abstract

Calorimetric measurements between 2 and 95 K show no specific-heat anomaly at the superconducting transition temperature of 28 K in ${\mathrm{La}}_{1.8}$ ${\mathrm{Ba}}_{0.2}$ ${\mathrm{CuO}}_{4\mathrm{-}\mathrm{y}}$ within our 1% resolution. This indicates that the total condensation energy associated with the superconducting transition is either very small, possibly resulting from only those electrons in interfacial (two-dimensional) layers, or zero as a result of a different mechanism for bulk superconductivity.