Spiral magnetism and chiral superconductivity in a Kondo-Hubbard triangular lattice model

Abstract

Building on the results of [Faye et al., Phys. Rev. B 97, 235151 (2018)], which identified an antiferromagnetic (AFM) and Kondo singlet phases on the Kondo-Hubbard square lattice, we use the variational cluster approximation to investigate the competition between these phases on a two-dimensional triangular lattice with 120o spin orientation. In addition to the AFM exchange interaction J⊥ between the localized (impurity) and conduction (itinerant) electrons, our model includes the local repulsion U of the conduction electrons and the Heisenberg interaction JH between the impurities. At half filling, we obtain the quantum phase diagrams in both planes (J⊥,UJ⊥) and (J⊥,JH). We identify a long-range, three-sublattice, spiral magnetic order which dominates the phase diagrams for small J⊥ and moderate U, while a Kondo singlet phase becomes more stable at large J⊥. The transition from the spiral magnetic order to the Kondo singlet phase is a second-order phase transition. In the (J⊥,JH) plane, we observe that the effect of JH is to reduce the Kondo singlet phase, giving more room to the spiral magnetic order phase. It also introduces some small magnetic oscillations of the spiral magnetic order parameter. At finite doping and when spiral magnetism is ignored, we find superconductivity with symmetry order-parameter d+id, which breaks time-reversal symmetry. The superconducting order parameter has a dome centered at around 5% hole doping, and its amplitude decreases with increasing J⊥. We show that spiral magnetism can coexist with d+id state and that superconductivity is suppressed, indicating that these two phases are in competition.

Similar papers