SPIN AND CHARGE SUSCEPTIBILITIES OF THE ATTRACTIVE HUBBARD CHAIN

The spin and charge susceptibilities of the attractive Hubbard chain a re obtained as a function of temperature, attractive interaction (-U) and band-filling solving numerically the thermodynamic Bethe-ansatz eq uations. The dominant states at low temperatures are spin-paired elect rons (like Cooper-pairs). The spin susceptibility is vanishingly small due to the spin gap and at half-filling it decreases with U. On the o ther hand, the charge susceptibility at half-filling increases with U and shows a maximum as a function of the band-filling, at constant T, which increases as T lowers and that shifts towards smaller values of the band-filling.