Intrinsic EPR in La2-xSrxCuO4: Manifestation of Three-Spin Polarons

Abstract

Electron-paramagnetic resonance (EPR) measurements on ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ provide experimental evidence of a three-spin polaron, consisting of two ${\mathrm{Cu}}^{2+}$ ions and one $p$ hole. The symmetry properties and the peculiar temperature dependence of the $g$ values of the EPR line indicate the presence of dynamical Jahn-Teller distortions and formation of a collective mode of polarons and surrounding strongly correlated Cu ions (bottlenecked regime).