Interaction-induced restoration of phase coherence

We study the conductance of a quantum "T junction" coupled to two electron reservoirs and a quantum dot. In the absence of electron-electron interactions, the conductance g is sensitive to interference between trajectories which enter the dot and those which bypass it. We show that including an intradot charging interaction has a marked influence. it can enforce a coherent response from the dot at temperatures much larger than the single-particle level spacing Delta. The result is large oscillations of g as a function of the voltage applied to a gate that is capacitively coupled to the dot. Without interactions, the conductance has only a weak interference signature when T > Delta.