Low-lying excited states,magnetic ordering and the phenomenology of the half-filled narrow-band metal-insulator transition at low temperature

A phenomenological theory is set up to take proper account of low-lying excited states in the vicinity of the metal-insulator transition in a half-filled narrow band at low temperature. The electronic specific heat is calculated and is shown to diverge as (1-U/U¹)^-1. Antiferromagnetic-ordering effects in the enhancement factor of the spin susceptibility are also discussed.