Topological quantum phase transition in Kane-Mele-Kondo lattice model

TL;DR

This paper investigates the phase diagram of the Kane-Mele-Kondo lattice model, revealing two antiferromagnetic phases, a topological quantum phase transition, and the absence of a quantum spin Hall insulator at the mean-field level.

Contribution

It introduces two new magnetic phases and characterizes a topological quantum phase transition within the Kane-Mele-Kondo lattice model, expanding understanding of its magnetic and topological properties.

Findings

Identified two antiferromagnetic spin-density-wave phases.

Discovered a topological quantum phase transition described by 3D quantum electrodynamics.

Found the quantum spin Hall insulator is unstable at the mean-field level.

Abstract

We systematically explore the ground-state phase diagram of the Kane-Mele-Kondo lattice model on the honeycomb lattice, in particular, we focus on its magnetic properties which has not been studied in the previous publication[Feng, Dai, Chung, and Si, Phys. Rev. Lett. \textbf{111}, 016402 (2013)]. Beside the Kondo insulator found in that paper, two kinds of antiferromagnetic spin-density-wave phases are identified. One is the normal antiferromagnetic spin-density-wave state and the other is a nontrivial topological antiferromagnetic spin-density-wave state with a quantized spin Hall conductance and a helical edge-state. The quantum spin Hall insulator is found to be absent since it is always unstable to antiferromagnetic spin-density-wave states at least at the mean-field level in our model. Furthermore, the transition between the two spin-density-wave phases are topological quantum phase transition described by the three-dimensional quantum electrodynamics, in which conduction electrons contribute to the low-energy Dirac fermions while the spin-wave fluctuation of local spins gives rise to an effective dynamic U(1) gauge-field. Such nontrivial transition shows radical critical thermodynamic, transport and single-particle behaviors, which provide a fingerprint for this transition. Additionally, the transition of antiferromagnetic spin-density-wave states to the Kondo insulator is found to be first-order. The introduction of two novel magnetic phases and their topological quantum phase transition show rich and intrinsic physics involving in the Kane-Mele-Kondo lattice model.