SPECTRAL PROPERTIES OF ONE-DIMENSIONAL INSULATORS AND SUPERCONDUCTORS

Conformal field theory and Bethe ansatz are used to investigate the lo w energy features of the spectral function in one dimensional models w hich exhibit a gap in the spin or in the charge excitation spectrum. E xotic behavior is found in the superconducting case, where the Green f unction displays momentum dependent Tomonaga-Luttinger liquid exponent s. The predictions of the formalism are confirmed by Lanczos diagonali zations in the t-J model up to 32 sites. These results may be relevant in connection to photoemission experiments in quasi-one-dimensional i nsulators or superconductors.