Explain the energy broadening discrepancy between experiment and DMRG

Explain the origin of the substantially broader energy spectrum observed in CeCo₂Ga₈ than in the DMRG simulations of the one-dimensional Kondo-Heisenberg model, including whether higher-dimensional electronic bands or the inaccessible regime 0 < J_H < J_k ≪ t is responsible.

Background

The neutron spectrum of CeCo₂Ga₈ is broader in energy than the spectra obtained from the one-dimensional DMRG calculations. Experimentally, the low-energy incommensurate fluctuations evolve smoothly into a finite-energy commensurate triplet resonance, whereas the simulations produce features that are more sharply separated in energy.

The paper identifies two possible explanations but does not resolve the issue: additional higher-dimensional electronic bands may broaden the spectrum, or the broadening may arise from the Kondo-Heisenberg model in the realistic weak-exchange regime 0 < J_H < J_k ≪ t, which the numerical calculations could not access. Determining the cause is important for assessing the quantitative validity of the minimal one-dimensional model for CeCo₂Ga₈.

References

The reason for this discrepancy is unknown---perhaps higher dimensional electronic bands cause this broadening (Quantum Monte Carlo calculations of 1D Heisenberg chain Kondo coupled to 2D electronic bands show much more dramatic broadening in energy ). Or perhaps this broadened spectrum is the behavior of the Kondo-Heisenberg model in the limit where $0 < J_H < J_k \ll t$, which our numerical calculations could not access.

— Incommensurate spin fluctuations in one-dimensional Kondo metal CeCo2Ga8  (2608.26071 - Huang et al., 26 Aug 2026) in Section Discussion, paragraph beginning “An important difference between theory and experiment”