The downward shift of the electron chemical potential m with hole doping in La 22x Sr x CuO 4 has been deduced from the shifts of photoemission and inverse-photoemission spectra. While the shift is large (ϳ1.5 eV͞hole) in overdoped samples, it is suppressed (,0.2 eV͞hole) in underdoped samples, implying a divergent charge susceptibility near the metal-insulator transition. In the overdoped regime, the m and the electronic specific heat coefficient g are consistently explained within

more »

... theory, whereas the same analysis gives unphysical results in the underdoped regime, indicating the breakdown of the Fermi-liquid picture in the underdoped regime. [S0031-9007(97)04058-1]