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

TL;DR

This study uses the density-matrix renormalization-group method to analyze how spin and charge gaps in a one-dimensional Kondo-lattice model depend on exchange interaction and Coulomb repulsion, revealing their growth and exponential decay behaviors.

Contribution

It provides a detailed numerical analysis of spin and charge gaps in the 1D Kondo-lattice model with Coulomb interaction, including their dependence on model parameters and asymptotic behaviors.

Findings

Both gaps increase with J and U_c.

Spin gap vanishes exponentially as J approaches zero.

Charge gap remains finite for U_c > 0 as J approaches zero.

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 $J \rightarrow 0$ for any $U_c$ with an exponential form, $\Delta_s\propto \exp{[-1/\alpha (U_c) J \rho]}$. The exponent, $\alpha (U_c)$, is determined as a function of $U_c$. The charge gap is generally much larger than the spin gap. In the limit of $J \rightarrow 0$, the charge gap vanishes as $\Delta_c=\frac{1}{2}J$ 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.