The one-dimensional Kondo lattice model at quarter-filling

TL;DR

This paper clarifies the existence of a dimerized phase with a non-zero charge gap in the quarter-filled one-dimensional Kondo lattice model, using accurate DMRG calculations to resolve previous conflicting claims.

Contribution

It demonstrates that previous objections against dimerization and charge gap were due to artificially suppressed dimer order, confirming their existence with precise numerical methods.

Findings

The dimerized phase exists at quarter-filling in the 1D Kondo lattice model.

The charge gap is confirmed to be non-zero in the dimerized phase.

Artificial suppression of dimer order can lead to incorrect conclusions.

Abstract

We revisit the problem of the quarter-filled one-dimensional Kondo lattice model, for which the existence of a dimerized phase and a non-zero charge gap had been reported in Phys. Rev. Lett. \textbf{90}, 247204 (2003). Recently, some objections were raised claiming that the system is neither dimerized nor has a charge gap. In the interest of clarifying this important issue, we show that these objections are based on results obtained under conditions in which the dimer order is artificially suppressed. We use the incontrovertible dimerized phase of the Majumdar-Ghosh point of the $J_{1}-J_{2}$ Heisenberg model as a paradigm with which to illustrate this artificial suppression. Finally, by means of extremely accurate DMRG calculations, we show that the charge gap is indeed non-zero in the dimerized phase.