The Fermi surface evolution in La2-xSrxCuO4

The Fermi surface (FS) of La2-xSrxCuO4 (LSCO) is investigated in the Hubbar d model by means of a first-order cumulant expansion. Despite the crudeness of our approximation. two important features of the real systems are descr ibed well. First. the doping dependence of the shape of the FS as observed by angle-resolved photoemission spectroscopy (ARPES) experiments on LSCO is obtained. Second, a possible interpretation of the sudden disappearance of the FS in the highly underdoped region is given. it is also shown as to ho w to reconcile the Luttinger's theorem (LT), that seems to be true in the o verdoped region, with the behaviour of the highly underdoped legion which i s evidently non-Fermi Liquid(FL) Like. Thus. we are able to explain why sma ll doping can product large FS. (C) 2000 Published by Elsevier Science B.V. All rights reserved.