The Coulomb blockade regime in disordered AlAs cleaved-edge overgrown quantum wires

We present transport measurements on AlAs quantum wires in the pinch-off regime, where the wire breaks up into zero-dimensional islands of electrons and Coulomb blockade sets in. Conductance resonances as a function of gate bias vanish at low temperature T, and a gap bounded by two peaks opens up in the differential conductance as a function of source-drain dc bias V. We propose two interpretations for these results: (i) low T, low V transport is limited by incoherent tunneling through 2 asymmetric quantum dots in series; (ii) at pinchoff the wire carries a collective mode that is pinned by disorder, but can be depinned by a finite threshold bias V.