Implications of infrared instability in a two-dimensional electron gas

We consider the tight-binding energy band in sq lattices and determine that in the half-filled case there exists an infrared instability in addition to the 2k/sub F/ (nesting)-type instability. In view of the pseudo-two-dimensional band structure of La/sub 2-//sub x/Ba/sub x/CuO4 recently proposed by Jorgensen et al. and by Mattheiss, our conclusions should be relevant to this material at least, one of which demonstrates the remarkable phenomenon of high-T/sub c/ superconductivity. To further analyze it, we devise a two-dimensional bosonization scheme. Three-dimensional bosonization is also briefly discussed