Abstract
Strong electron correlations can give rise to extraordinary properties of metals with renormalized Landau quasiparticles. Near a quantum critical point, these quasiparticles can be destroyed and non-Fermi liquid behavior ensues. YbRh2Si2 is a prototypical correlated metal exhibiting the formation of quasiparticle and Kondo lattice coherence, as well as quasiparticle destruction at a field-induced quantum critical point. Here we show how, upon lowering the temperature, Kondo lattice coherence develops at zero field and finally gives way to non-Fermi liquid electronic excitations. By measuring the single-particle excitations through scanning tunneling spectroscopy, we find the Kondo lattice peak displays a non-trivial temperature dependence with a strong increase around 3.3 K. At 0.3 K and with applied magnetic field, the width of this peak is minimized in the quantum critical regime. Our results demonstrate that the lattice Kondo correlations have to be sufficiently developed before quantum criticality can set in.
Highlights
Strong electron correlations can give rise to extraordinary properties of metals with renormalized Landau quasiparticles
The on-site Kondo effect causes a hybridization between the 4f and the conduction electrons, which eventually screens the local moments by developing Kondo spin-singlet many-body states
Spectra obtained at temperatures T ≥ 4.6 K and H = 0 revealed the successive depopulation of the excited crystalline electric field (CEF) states as the temperature is lowered, with essentially only the lowest crystalfield Kramers doublet occupied at lowest temperatures[7]
Summary
Strong electron correlations can give rise to extraordinary properties of metals with renormalized Landau quasiparticles. YbRh2Si2 is a prototypical correlated metal exhibiting the formation of quasiparticle and Kondo lattice coherence, as well as quasiparticle destruction at a field-induced quantum critical point. Upon lowering the temperature, Kondo lattice coherence develops at zero field and gives way to nonFermi liquid electronic excitations. The on-site Kondo effect causes a hybridization between the 4f and the conduction electrons, which eventually screens the local moments by developing Kondo spin-singlet many-body states. These two interactions directly compete with each other and lead to different (long-range magnetically ordered vs paramagnetic Fermi-liquid) ground states[3]. The coupling between the localized 4f electrons in this Kramers doublet and the conduction electrons gives rise to periodic Kondo-singlet correlations which start to develop below Tcoh
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