On the origin of the lambda-type transition in heat capacity

Abstract

The lambda-type transition in the variation of heat capacity with temperature consists of a narrow asymmetric maximum in phonon-driven heat capacity. Although it was not so labeled at the time, “the specific heat singularity in solid NH 4Cl", obtained by Simon in 1922 was the first true λ -anomaly to be discovered. Thereafter, the transition was discovered over a period of years in several cases. Sometime along the way, probably after its discovery in 4He, it became identified as the lambda-type transition. Analyses of the anomaly are effected in an attempt to find its origin and the parameters that characterize it.