Quantum theory of solid-liquid coexistence and interface inHe4

We present a variational Monte Carlo simulation of solid-liquid coexistence and interface in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ at T=0 K. We employ a new, generalized form of the shadow wave function in which intershadow correlations are made explicitly dependent on a local density operator. This form allows for a unique representation of the ground state for the whole range of density extending over the two phases. In the phase transition region the stable state consists of a slab of crystal coexisting with the fluid. We obtain the local density, the order parameter, and the interfacial energy for the {100} surface of an fcc crystal.