A spin polaron in a two-dimensional antiferromagnet: From a local singlet to a complex quasiparticle

We set forth basic theoretical ideas concerning the spin-polaron scenario for charge excitations in a two-dimensional antiferromagnet. A distinctive feature of the approach being developed consists in considering a local polaron (rather than a bare hole) as a zero approximation for the quasiparticle. At the next step, this excitation is dressed in antiferromagnetic spin waves to form a polaron of intermediate (or infinite) radius. The method allows us to continuously describe the transition from zero to finite temperatures and to consider a wide doping range. Our approach accounts for the main results of ARPES experiments in a CuO$_2$ plane.