Quantum phase transitions, frustration, and the Fermi surface in the Kondo lattice model

TL;DR

This study investigates the quantum phase transition in a one-dimensional Kondo-Heisenberg model, revealing a continuous transition with an intermediate phase, challenging traditional local picture assumptions in heavy fermion systems.

Contribution

It demonstrates a continuous quantum phase transition with an intermediate phase in a 1D Kondo lattice model, using DMRG, contrasting with the local picture predictions.

Findings

Transition is continuous with an intermediate phase

Intermediate phase is spin gapped with incommensurate correlations

Results challenge the local picture of Fermi surface change

Abstract

The quantum phase transition from a spin-Peierls phase with a small Fermi surface to a paramagnetic Luttinger-liquid phase with a large Fermi surface is studied in the framework of a one-dimensional Kondo-Heisenberg model that consists of an electron gas away from half filling, coupled to a spin-1/2 chain by Kondo interactions. The Kondo spins are further coupled to each other with isotropic nearest-neighbor and next-nearest-neighbor antiferromagnetic Heisenberg interactions which are tuned to the Majumdar-Ghosh point. Focusing on three-eighths filling and using the density-matrix renormalization-group (DMRG) method, we show that the zero-temperature transition between the phases with small and large Fermi momenta appears continuous, and involves a new intermediate phase where the Fermi surface is not well defined. The intermediate phase is spin gapped and has Kondo-spin correlations that show incommensurate modulations. Our results appear incompatible with the local picture for the quantum phase transition in heavy fermion compounds, which predicts an abrupt change in the size of the Fermi momentum.