Anisotropic hybridization dynamics in the quasi-one-dimensional Kondo lattice CeCo₂Ga₈ revealed by ultrafast optical spectroscopy

Abstract

We investigate the ultrafast dynamics of the quasi-one-dimensional Kondo lattice CeCo₂Ga₈ using optical pump-probe spectroscopy. Time-resolved pump-probe reflectivity measurements reveal a strong anisotropy in the photoinduced response, which is a direct consequence of the material’s unique electronic structure. The temperature dependence of the relaxation dynamics provides evidence for the formation of two distinct hybridization gaps that appear at different temperatures in the heavy fermion state. A direct gap of 2{\mathrm{\Delta }}_{dir}\approx 50 meV that persists up to T^{†}\approx 90 K, well above the coherence temperature T^{\ast }\approx 20 K. We attribute this higher-temperature gap to the hybridization fluctuations. An indirect gap of 2{\mathrm{\Delta }}_{ind}\approx 14 meV opens closer to T^{\ast }, signifying the development of long-range coherence in the heavy fermion state. Furthermore, we find that the hybridization gap can be suppressed with increasing pump fluence, indicating a delicate interplay between photoexcitation and the coherent heavy fermion state. Our results provide insights into the interplay of Kondo physics and low dimensionality in CeCo₂Ga₈, and establish ultrafast optical spectroscopy as a sensitive probe of anisotropic hybridization in heavy fermion materials.

Graphical abstract

Keywords

hybridization / heavy fermion / ultrafast optical spectroscopy / quasi-one-dimensional

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Declarations

The authors declare that they have no competing interests and there are no conflicts.

Electronic supplementary materials

The online version contains supplementary material available at https://doi.org/10.15302/frontphys.2025.044208.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant Nos. 12074436, U22A6005, and U2032204), the National Key Research and Development Program of China (Grant No. 2022YFA1604204), the Science and Technology Innovation Program of Hunan Province (No. 2022RC3068), and the Natural Science Foundation of Changsha (No. kq2208254).

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