The ground state of binary boson mixtures

Abstract

We consider the ground-state configurations of mixtures of strongly interacting bosons using a variational ansatz: the average correlation approximation (ACA). Using this ansatz, we are able to obtain explicit expressions for the first and second concentration derivatives of the enthalpy which can then be used to interpret the detailed numerical results. The range of ACA accuracy is ascertained by examining the mixtures in the weakly correlated limit. For those systems for which the potential energy core sizes are equal, the ACA gives reliable enthalpy upper bounds and second derivatives. A detailed comparative analysis is made between mixture calculations at fixed pressure and mixture calculations at fixed volume. A hard-sphere boson mixture is used to illustrate relevant points.