Formation and local symmetry of Holstein polaron in t-J model
  The formation and local symmetry of spin-lattice polaron has been investigated semiclassically in the planar Holstein t-J-like models within the exact diagonalization method. Due to the interplay of strong correlations and electron-lattice interaction, the doped hole may either move freely or lead to the localized spin-lattice distortion and form a Holstein polaron. The formation of polaron breaks the translational symmetry by suppression of antiferromagnetic correlations and inducement of ferromagnetic correlations locally. Moreover, the breaking of local rotational symmetry around the polaron has been shown. The ground state is generically a parity singlet and the first excited state maybe a parity doublet. Further consequences of the density of states spectra for comparison with future STM experiments are discussed. 
Han Ma, T. K. Lee, and Yan Chen
cond-mat.str-el cond-mat.supr-con