Quantum phase transition in a two-channel-Kondo quantum dot device

We develop a theory of electron transport in a double quantum dot device recently proposed in [Y. Oreg and D. Goldhaber-Gordon, Phys. Rev. Lett. 90, 136602 (2003)] for the observation of the two-channel Kondo effect. Our theory provides a strategy for tuning the device to the non-Fermi-liquid fixed point, which is a quantum critical point in the space of device parameters. We explore the corresponding quantum phase transition, and make explicit predictions for behavior of the differential conductance in the vicinity of the quantum critical point.