Dilute quantum liquid in a K-Rb Bose mixture

A quantum liquid in a heterogeneous mixture of and atoms is studied using the diffusion Monte Carlo method and density-functional theory. The perturbative Lee-Huang-Yang term for a heterogeneous mixture is verified and it is proved to be valid only near the gas-liquid transition. Based on the equations of state of the bulk mixture, calculated with diffusion Monte Carlo, extensions to Lee-Huang-Yang corrected mean-field energy functionals are presented. Using density-functional theory, a systematic comparison between different functionals is performed, focusing on the critical atom number, surface tension, surface width, Tolman length, and compressibility. These results are given as a function of the interspecies interaction strength, within the stability domain of the liquid mixture.