Large-Nlimit of a magnetic impurity in unconventional density waves

Abstract

We investigate the effect of unconventional density wave ͑UDW͒ condensate on an Anderson impurity using large-N technique at T = 0. In accordance with previous treatments of a Kondo impurity in pseudogap phases, we find that Kondo effect occurs only in a certain range of parameters. The f-electron density of states reflects the influence of UDW at low energies and around the maximum of the density wave gap. The static spin susceptibility diverges at the critical coupling, indicating the transition from strong to weak coupling. In the dynamic spin susceptibility an additional peak appears showing the presence of the of UDW gap. Predictions concerning nonlinear density of states are made. Our results apply to other unconventional condensates such as d-wave superconductors and d-density waves as well.

Quantum impurity in the bulk of a topological insulator

“…This kind of narrow mixed-valence regime has also been found in unconventional density waves and d-wave superconductors. 28,31 For mB < 0, the density of states of bulk electrons vanishes at the band edges. The reduction of the density of states at the band edges implies that the Kondo resonance peak is narrower and b 2 0 decreases to zero faster than those in the conventional case.…”

“…For mB > 0, the bound states are very close to the band edges when˜ d is far away from the energy gap. In the previous studies, [31][32][33] it has been argued that, when the energy gap exceeds a critical value ( /T K = 2.0 predicted by slave-boson mean-field theory 32 and T K is the Kondo temperature), the Kondo effect no longer appears in insulators with an energy-independent density of states. However, for a complex dispersion relation, the density of states is strongly energy resolved and quite different near the band edges for the band-inverted and normal cases.…”

“…The study of quantum impurities in TIs is also related to the problems of impurities in unconventional density waves, [28][29][30][31] gapped systems, 32,33 or spin-orbit-coupled systems. [34][35][36] For instance, in a gapped system, the Kondo effect breaks down when the energy gap exceeds a critical value.…”

Reentrant Kondo effect in Landau-quantized graphene: Influence of the chemical potential

“…The 1/(N + 1) ∝ B prefactor denotes the Landau level degeneracy. These reduce to the standard saddle-point equations for gapless phases 28,30 for zero field and Γ = 0. The extra factor of 2 in front of V 2 stems from the two non-equivalent Dirac cones at the K and K ′ points, since by using…”