Modulated spiral order in the 1D Kondo lattice model

Abstract We have analyzed magnetic order in the one-dimensional Kondo lattice with classical localized spins. To identify relevant low-energy configurations, we combine the exact diagonalization of the electronic system with a dissipative evolution, described by the Landau–Lifshitz-Gilbert equation. We find that spiral states always relax into a more complex form of noncollinear order, characterized by a periodic modulation of the relative angles between neighboring spins. A finite-size scaling analysis shows that the amplitude of the modulation and the gain in free energy remain finite in the thermodynamic limit. Importantly, the wavelength of the modulation is determined by the Fermi wavevector of the unperturbed spiral. This suggests that complex noncollinear order originates from an instability of the unperturbed spirals, which, in the presence of a weak pairing term, may hinder topological superconductivity. Our final phase diagram is obtained by comparing the modulated spiral states with various complex collinear configurations proposed in the literature.