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In strongly correlated electronic systems the excitation gap is originated by a spontaneous symmetry breaking and usually it develops only for one degree of freedom: charge for magnetic or Mott insulators and spin for singlet states. Then the fate of embedded electrons or holes (doping, tunneling, photoemission, optics, field effect) is to separate their charge and spin quantum numbers to different reservoirs. The effect is well established theoretically and experimentally in one dimensional 1D systems where solitons emerge as elementary excitations. They have been observed in conducting polymers, spin-Peierls chains, organic metals, Charge- and Spin Density Waves. In the general 2D or 3D world, these topologically nontrivial states experience the confinement resulting in a particular spin-charge recombination. It originates the spin- or charge- roton like configurations with charge- or spin- kinks localized in the core, correspondingly for cases of repulsion and attraction. Thus for the doped Mott insulator the spin-roton complex assists the holon propagation. For superconductors we find a p- vortex ring with the spinon bound to its center; here the spinon functions as the single electronic p- junction. These excitations can be also viewed as the nucleus of the melted stripe phase which is typically observed under higher doping or of the FFLO phase in spin polarized superconductors. The crossover from bare band states to these combined quasi particles can describe the pseudogaps observed in tunneling, optics, photoemission. REFERENCES: cond-mat/0006355/0004313/9911143/0204147 |