Spin and charge gaps in the one-dimensional Kondo-lattice model with Coulomb interaction between conduction electrons

Abstract

The density-matrix renormalization-group method is applied to the one-dimensional Kondo-lattice model with the Coulomb interaction between the conduction electrons. The spin and charge gaps are calculated as a function of the exchange constant $J$ and the Coulomb interaction $U_c$. It is shown that both the spin and charge gaps increase with increasing $J$ and $U_c$. The spin gap vanishes in the limit of $J\to 0$ for any $U_c$ with an exponential form, $\hat{I}{”}_s\propto \exp [-1/\hat{I}\pm (U_c)J\ddot{I}]$. The exponent, $\hat{I}\pm (U_c)$, is determined as a function of $U_c$. The charge gap is generally much larger than the spin gap. In the limit of $J\to 0$, the charge gap vanishes as $\hat{I}{”}_c=\frac{1}{2}J$ for $U_c=0$ but for a finite $U_c$ it tends to a finite value, which is the charge gap of the Hubbard model.

RevTeX, 4 pages, 3 Postscript figures