Fermi Surface Instability of Quasi-Two-Dimensional Tight Binding Electrons : A Possible Phase Diagram of (La1-xMx)₂CuO₄

The Hartree-Fock instability against charge or spin density wave is examined as a function of the band filling for quasi-two-dimensional tight binding electrons in the tetragonal symmetry. It is found that the existence of the instability can be confined to the region close to the half-filling. The implication of the present result is discussed in the context of high T c superconductor, (La 1- x M x ) 2 CuO 4 , and it is indicated that the ground state for very small value of x will be the spin density wave (SDW) and that the superconductivity state is stabilized above some critical value of x of the order of 0.01.