Physical Review Letters
Susceptibility singularities at first-order phase transitions
Douglas B. Abraham, Paul J. Upton
Abstract
The bubble picture for pair-spin correlation functions is applied to two-dimensional Ising-like models, at subcritical temperatures, in an external field h, from which we show, via the fluctuation sum, that the susceptibility \ensuremath{\chi}(h) has an essential singularity at h=0. This is studied further using a solid-on-solid bubble model for (a) a restricted ensemble corresponding to metastability, where h=0 is found to be the limit point of an infinite number of poles of \ensuremath{\chi} along the negative real axis, and (b) an unrestricted ensemble, where a Yang-Lee circle theorem is found.