Transport Spectroscopy of Coupled Quantum Dots in Conditions of the Kondo Effect

We develop electron transport theory for novel devices [1,2], which are interesting in the context of correlated electrons physics. The device proposed in Ref. [1] is designed for an observation of a non-Fermi-liquid behavior of itinerant electrons. The device measured in Ref. [2] may serve a similar purpose, and also may become important for quantum computing.\\ In the case of Ref. [1], our theory [3] provides a strategy for tuning to the non-Fermi-liquid fixed point -- a quantum critical point in the space of device parameters. We explore the corresponding quantum phase transition, and make explicit predictions for the behavior of differential conductance in the vicinity of the quantum critical point. \\ Motivated by the measurements [2], we developed a theory of conductance of Kondo quantum dots coupled by the RKKY interaction [4]. Investigation of the differential conductance at fixed interaction strength may allow one to distinguish between the possible ground states of the system. Transition between the ground states is achieved by tuning the interaction strength; the nature of the transition (which includes a possibility of a non-Fermi-liquid point) can be extracted from the temperature dependence of the linear conductance.\\ This research is supported by NSF grants DMR02-37296 and EIA02- 10736.\\ 1. Y. Oreg and D. Goldhaber-Gordon, Phys. Rev. Lett. {\bf 90}, p. 136602 (2003). \\ 2. N.J. Craig J.M. Taylor, E.A. Lester, C.M. Marcus, M.P. Hanson, and A.C. Gossard, Science {\bf 304}, 565 (2004).\\ 3. M.G. Vavilov and L.I. Glazman, preprint cond-mat/0404366.\\ 4. M. Pustilnik, L. Borda, L.I. Glazman, and J. von Delft, Phys. Rev. {\bf B 69}, 115316 (2004).