Do quantum dots allow one access to pseudogap Kondo physics?

For the last decade (Phys. World 14 (1) (2001) 33), tunable quantum dot systems have allowed the investigation of Kondo physics wherein the quenching of a single spin on an artificial atom affects the conductance. The pseudogap Kondo model (pKm) featuring a density of states ρ ( ε ) = C | ε | r , introduced by Withoff and Fradkin (Phys. Rev. Lett. 64 (1990) 1835) in 1990 was predicted to exhibit Kondo-like physics above a critical value of the Kondo coupling, J c , which several groups have shown by numerical renormalization group (RG) is finite for r < 1 2 . Gonzalez-Buxton et al. (Phys. Rev. B 57 (1998) 14254) showed that the strong coupling limit of the particle–hole symmetric model leads to a non-trivial π ( 1 - r ) / 2 phase shift at low temperatures, indicating incomplete screening of the local moment, while away from particle–hole symmetry (p–hs) one generically flows towards a ground state with δ ∼ π . We examine the implications of this model for quantum dots whose leads are Fermi liquid-like, yet possess a tunneling density of states (TDOS) which is suppressed at the Fermi energy as a power law.