THEORY OF STRONG INELASTIC COTUNNELING

We develop a theory of the conductance of a quantum dot connected to t wo leads by single-mode quantum point contacts. If the contacts are in the regime of perfect transmission, the conductance shows no Coulomb blockade oscillations as a function of the gate voltage. In the presen ce of small reflection in both contacts, the conductance develops smal l Coulomb blockade oscillations. As the temperature of the system is l owered, the amplitude of the oscillations grows, and eventually sharp periodic peaks in conductance are formed. Away from the centers of the peaks the conductance vanishes at low temperatures as T-2, in agreeme nt with the theory of inelastic cotunneling developed for the weak-tun neling case. Conductance near the center of a peak can be studied usin g an analogy with the multichannel Kondo problem. In the case of symme tric barriers, the peak conductance at T --> 0 is of the order of <e(2 )/(h)over bar>. In the asymmetric case, the peak conductance vanishes linearly in temperature.