Signatures of quantum phase transitions in parallel quantum dots:   Crossover from local-moment to underscreened spin-1 Kondo physics
  We study a strongly interacting "quantum dot 1" and a weakly interacting "dot 2" connected in parallel to metallic leads. Gate voltages can drive the system between Kondo-quenched and non-Kondo free-moment phases separated by Kosterlitz-Thouless quantum phase transitions. Away from the immediate vicinity of the quantum phase transitions, the physical properties retain signatures of first-order transitions found previously to arise when dot 2 is strictly noninteracting. As interactions in dot 2 become stronger relative to the dot-lead coupling, the free moment in the non-Kondo phase evolves smoothly from an isolated spin-one-half in dot 1 to a many-body doublet arising from the incomplete Kondo compensation by the leads of a combined dot spin-one. These limits, which feature very different spin correlations between dot and lead electrons, can be distinguished by weak-bias conductance measurements performed at finite temperatures. 
Arturo Wong, W. Brian Lane, Luis G. G. V. Dias da Silva, Kevin   Ingersent, Nancy Sandler, and Sergio E. Ulloa
cond-mat.str-el cond-mat.mes-hall