title: Low-energy spectra in t-J-type models at low doping levels.
abstract: Based on a variational approach, we propose that there are two kinds of low-energy states in the t-J-type models at low doping. In a quasiparticle state an unpaired spin bound to a hole with a well-defined momentum can be excited with spin waves. The resulting state shows a suppression of antiferromagnetic order around the hole with the profile of a spin bag. These spin-bag states with spin and charge or hole separated form a continuum of low-energy excitations. Very different properties predicted by these two kinds of states explain a number of anomalous results observed in the exact diagonalization studies on small clusters up to 32 sites.
authors.affiliation: Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan 11529.
authors.forename: Wei-Cheng
authors.initials: WC
authors.lastname: Lee
authors.forename: T K
authors.initials: TK
authors.lastname: Lee
authors.forename: Chang-Ming
authors.initials: CM
authors.lastname: Ho
authors.forename: P W
authors.initials: PW
authors.lastname: Leung