Unveiling the Hybridization Process in a Quantum Critical Ferromagnet by Ultrafast Optical Spectroscopy

Abstract

We report the ultrafast optical pump-probe spectroscopy measurements on the recently discovered quantum critical ferromagnet CeRh${}_6$Ge${}_4$. Our experimental results reveal the two-stage development of the hybridization between localized $f$ moments and conduction electrons with lowering temperature, as evidenced by (1) the presence of hybridization fluctuation for temperatures from $\sim$85 K ($T^{\ast }$) to $\sim$140 K ($T^{†}$), and (2) the emergence of collective hybridization below the coherence temperature, $T^{\ast }$, marked by the opening of an indirect gap of 2$\Delta$ $\approx$12 meV. We also observe three coherent phonon modes being softened anomalously below $T^{\ast }$, reflecting directly their coupling with the emergent coherent heavy electrons. Our findings establish the universal nature of the hybridization process in different heavy fermion systems.

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Cited by in corpus (10)

• A unified theory of ferromagnetic quantum phase transitions in heavy fermion metals
• Coupling of optical phonons with Kondo effect and magnetic orders in antiferromagnetic Kondo lattice CeAuSb${}_2$
• Probing quantum criticality in ferromagnetic CeRh6Ge4
• Development of long-range phase coherence on the Kondo lattice
• Suppression of ferromagnetism and influence of disorder in silicon-substituted CeRh6Ge4
• An emerging global picture of heavy fermion physics
• Relocalization of Uranium 5f Electrons in Antiferromagnetic Heavy Fermion Superconductor UPd${}_2$Al${}_3$: Insights from Angle-Resolved Photoemission Spectroscopy
• Ultrafast Stiffening of the Lattice Potential and Metastable State Formation in 1$T$-TiSe${}_2$
• Fingerprints for anisotropic Kondo lattice behavior in the quasiparticle dynamics of the kagome metal Ni${}_3$In
• Non-collinear ferromagnetism in the Kondo lattice Ce${}_5$CoGe${}_2$