Coupled dimer and bond-order-wave order in the quarter-filled one-dimensional Kondo lattice model

TL;DR

This study investigates the ground state of a quarter-filled one-dimensional Kondo lattice model, revealing a coupled dimer and bond-order-wave phase that explains experimental observations of simultaneous Peierls and spin-Peierls transitions.

Contribution

It demonstrates the existence of a coupled dimer and BOW state in the weak coupling regime and characterizes the quantum phase transition at a critical coupling, advancing understanding of related experimental phenomena.

Findings

Identification of a coupled dimer and BOW phase at weak coupling.

Quantum phase transition occurs at a critical coupling J_c with a charge gap opening.

Localized spins exhibit quasi-long ranged collinear correlations resembling classical dimer order.

Abstract

Motivated by the experiments on the organic compound $(Per)_{2}[Pt(mnt)_{2}]$, we study the ground state of the one-dimensional Kondo lattice model at quarter filling with the density matrix renormalization group method. We show a coupled dimer and bond-order-wave (BOW) state in the weak coupling regime for the localized spins and itinerant electrons, respectively. The quantum phase transitions for the dimer and the BOW orders occur at the same critical coupling parameter $J_{c}$, with the opening of a charge gap. The emergence of the combination of dimer and BOW order agrees with the experimental findings of the simultaneous Peierls and spin-Peierls transitions at low temperatures, which provides a theoretical understanding of such phase transition. We also show that the localized spins in this insulating state have quasi-long ranged spin correlations with collinear configurations, which resemble the classical dimer order in the absence of a magnetic order.