“…Hence some mathematicians considered equation (1) by studying some constrained variational problems and obtained the existence of ground state of equation (1). This technique was generally used for other types of equations, for example, semilinear Schrödinger equation [11,24], Schrödinger-Poisson equation [4,12], quasilinear Schrödinger equation [29,30]; see also [1,2,18,21,22]. For s = 1, as far as we know, the first work comes from Ye [25], who considered the following minimization problem:…”