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TT: Fachverband Tiefe Temperaturen

TT 98: Focus Session: Visualization of Heavy Fermion Formation through Scanning Tunneling Microscopy

TT 98.4: Topical Talk

Donnerstag, 19. März 2015, 16:45–17:15, H 0104

Developing Kondo Lattice Coherence and Quantum Criticality in YbRh₂Si₂ — •Steffen Wirth¹, Silvia Seiro¹, Stefan Kirchner², Cornelius Krellner³, Christoph Geibel¹, Qimiao Si⁴, and Frank Steglich¹ — ¹MPI for Chemical Physics of Solids, Dresden, Germany — ²MPI for Physics of Complex Systems, Dresden, Germany — ³Goethe University Frankfurt, Germany — ⁴Rice University, Houston, Texas, USA

Hybridization is a fundamental concept in strongly correlated electron physics. In heavy fermion metals, it may result in the generation of low-energy scales that can give rise to quantum criticality and unconventional superconductivity. An important techniques that helped shaping our understanding of nonlocal correlations – magnetic and superconducting – has been tunneling spectroscopy (STS) with its unique ability to give local, microscopic information that directly relates to the one-particle Green’s function. We investigated YbRh₂Si₂, an archetypal heavy fermion metal. Quantum criticality is discussed in terms of an antiferromagnetic instability and a Kondo break-down of the heavy quasiparticles. STS studies identified a hybridization-induced gap-like feature of the tunneling conductance. Here we focus on the evolution of the Kondo lattice. While the Kondo lattice starts forming already at the single-ion Kondo temperature, lattice Kondo effects dominate only at much lower temperatures. This establishes a hierarchy of energy scales. Finite-temperature signatures of the QCP are observed in field-dependent STS. Our findings are augmented by band structure calculations and transport measurements.