Abstract Submitted for the MAR08 Meeting of The American Physical Society Finite-temperature conductance signatures of a quantum-critical transition in a double quantum-dot device1

Submitted for the MAR08 Meeting of The American Physical Society Finite-temperature conductance signatures of a quantum-critical transition in a double quantum-dot device1 NANCY SANDLER, Ohio University, LUIS DIAS DA SILVA, Oak Ridge Natl. Lab. and U. of Tennessee, KEVIN INGERSENT, U. of Florida, SERGIO ULLOA, Ohio University — We present conductance results for a quantum-dot system containing one dot in the Kondo regime coupled to two leads in parallel with a noninteracting resonant level. The system can be mapped onto a single-impurity Anderson model with a pseudogapped effective density of states [1]. The finite-temperature linear conductance G(T ) of this double-dot device is obtained via numerical renormalization-group calculations. The position of the single-particle levels can be controlled with gate voltages so that the effective density of states vanishes in power-law fashion at the Fermi energy of the leads; within this regime, further tuning can drive the system through a quantum critical point separating Kondo and unscreened phases. Signatures of both effects appear in G(T ), with a prominent feature at the scale T ∗ marking the crossover from the high-temperature quantum-critical regime to a low-temperature Fermi liquid. These results open the way for experimental verification of the effect, and in principle allow access to a quantum critical point in a unique tunable system. [1] L.G.G.V. Dias da Silva et al., PRL 97, 096603 (2006). 1Supported in part by NSF DMR–0312939 and NSF-IMC/NIRT. Luis Dias da Silva Oak Ridge Natl. Lab Date submitted: 30 Nov 2007 Electronic form version 1.4