Visualizing heavy fermions emerging in a quantum critical Kondo lattice

Abstract

In solids containing elements with f orbitals, the interaction between f-electron spins and those of itinerant electrons leads to the development of low-energy fermionic excitations with a heavy effective mass. These excitations are fundamental to the appearance of unconventional superconductivity and non-Fermi-liquid behaviour observed in actinide- and lanthanide-based compounds. Here we use spectroscopic mapping with the scanning tunnelling microscope to detect the emergence of heavy excitations with lowering of temperature in a prototypical family of cerium-based heavy-fermion compounds. We demonstrate the sensitivity of the tunnelling process to the composite nature of these heavy quasiparticles, which arises from quantum entanglement of itinerant conduction and f electrons. Scattering and interference of the composite quasiparticles is used to resolve their energy-momentum structure and to extract their mass enhancement, which develops with decreasing temperature. The lifetime of the emergent heavy quasiparticles reveals signatures of enhanced scattering and their spectral lineshape shows evidence of energy-temperature scaling. These findings demonstrate that proximity to a quantum critical point results in critical damping of the emergent heavy excitation of our Kondo lattice system.

preprint version, 26 pages, 6 figures. Supplementary: 15 pages, 14 figures

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Cited by in corpus (7)

• Hybridization, Inter-Ion Correlation, and Surface States in the Kondo Insulator SmB6
• Microwave spectroscopy on heavy-fermion systems: probing the dynamics of charges and magnetic moments
• Challenging Magnetic Field Dependence of the Residual Resistivity of the Heavy-Fermion Metal CeCoIn5
• Terahertz Conductivity of the Heavy-Fermion State in CeCoIn5
• Nature of the quantum critical point as disclosed by extraordinary behavior of magnetotransport and the Lorentz number in the heavy-fermion metal YbRh2Si2
• Scanning tunneling microscopy with InAs nanowire tips
• Spectral changes in layered $f$-electron systems induced by Kondo hole substitution in the boundary-layer