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Authors: S. Wirth, S. Ernst, S. Kirchner, C. Krellner, C. Geibel, G. Zwicknagl and F.
Steglich
Heavy fermion metals are often characterized by a variety of relevant energy scales and competing interactions which may result in such fascinating phenomena as quantum criticality and unconventional superconductivity. Therefore, these materials have advanced to suitable model systems by means of which electronic interactions can be studied in detail. This will be discussed for the interplay of localized and itinerant electronic states in Kondo lattice systems in which heavy charge carriers are generated. We investigate the generic Kondo lattice system YbRh2Si2, one of the heaviest heavy fermion metals, by utilizing atomically resolved Scanning Tunneling Spectroscopy (STS). The hybridization of conduction and 4f electrons results in a gap-like feature in the tunneling conductance. In addition, the crystal field excitations are unambiguously reflected by STS for the first time. A strongly temperature dependent peak in tunneling conductance is attributed to a resonance resulting from the Kondo lattice. The experimental data are discussed in relation to results obtained within the non-crossing approximation (NCA) and renormalized band structure calculation. In a brief outlook we discuss possible further investigations by STS with respect to doping-related disorder as well as quantum criticality in YbRh2Si2. |
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