Differential Conductance and Quantum Interference in Kondo Systems

We present a large-N theory for the differential conductance, dI/dV, in Kondo systems measured via scanning tunneling spectroscopy. We demonstrate that quantum interference between tunneling processes into the conduction band and into the magnetic f-electron states is crucial in determining the experimental Fano lineshape of dI/dV. This allows one to uniquely extract the Kondo coupling and the ratio of the tunneling amplitudes from the experimental dI/dV curve. Finally, we show that dI/dV directly reflects the strength of the antiferromagnetic interaction in Kondo lattice systems.Comment: 4 pages, 4 figure

Defects in Heavy-Fermion Materials: Unveiling Strong Correlations in Real Space

Complexity in materials often arises from competing interactions at the atomic length scale. One such example are the strongly correlated heavy-fermion materials where the competition between Kondo screening and antiferromagnetic ordering is believed to be the origin of their puzzling non-Fermi-liquid properties. Insight into such complex physical behavior in strongly correlated electron systems can be gained by impurity doping. Here, we develop a microscopic theoretical framework to demonstrate that defects implanted in heavy-fermion materials provide an opportunity for unveiling competing interactions and their correlations in real space. Defect-induced perturbations in the electronic and magnetic correlations possess characteristically different spatial patterns that can be visualized via their spectroscopic signatures in the local density of states or non-local spin susceptibility. These real space patterns provide insight into the complex electronic structure of heavy-fermion materials, the light or heavy character of the perturbed states, and the hybridization between them. The strongly correlated nature of these materials also manifests itself in highly non-linear quantum interference effects between defects that can drive the system through a first-order phase transition to a novel inhomogeneous ground state.Comment: 11 pages, 7 figure

Disorder and quasiparticle interference in heavy-fermion materials

Using a large-N approach, we study the effect of disorder in the Kondo-screened phase of heavy-fermion materials. We demonstrate that the strong feedback between the hybridization and the conduction electron charge density magnifies the effect of disorder, such that already small concentrations of defects strongly disorder the materials' local electronic structure, while only weakly affecting their spatially averaged, thermodynamic properties. Finally, we show that the microscopic nature of defects can be identified through their characteristic signatures in the hybridization and quasiparticle interference spectrum.Comment: 5 pages; v2: published versio

Hidden Order Transition in URu2Si2 and the Emergence of a Coherent Kondo Lattice

Using a large-N approach, we demonstrate that the differential conductance and quasi-particle interference pattern measured in recent scanning tunneling spectroscopy experiments (A.R. Schmidt et al. Nature 465, 570 (2010); P. Aynajian et al., PNAS 107, 10383 (2010)) in URu2Si2 are consistent with the emergence of a coherent Kondo lattice below its hidden order transition (HOT). Its formation is driven by a significant increase in the quasi-particle lifetime, which could arise from the emergence of a yet unknown order parameter at the HOT.Comment: 5 pages, 3 figure

Hidden order transition in URu2Si2: Evidence for the emergence of a coherent Anderson lattice from scanning tunneling spectroscopy

Using a slave-boson approach, we demonstrate that the differential conductance and quasiparticle interference pattern measured in recent scanning tunneling spectroscopy experiments [Schmidt et al., Nature (London) 465, 570 (2010); Aynajian et al., Proc. Natl. Acad. Sci. USA 107, 10383 (2010)] in URu2Si2 are consistent with the emergence of a coherent Anderson lattice below the hidden order transition (HOT). Its formation is driven by a significant increase in the quasiparticle lifetime, which could arise from the emergence of a yet unknown order parameter at the HOT