Electron coupling in weakly and strongly coupled quantum point contacts

We present electron transport investigations in coupled double quantum point contacts defined by a split gate on the top of a novel narrow-barrier double-quantum-well structure. Using different barrier heights between the wells, we fabricated devices with strong and weak coupling. Mixing of the wavefunctions occurs in the strong coupling device with an (Al,Ga)As barrier, We are able to determine the sublevel spacing energy as well as the symmetric-antisymmetric sublevel splitting energy Delta (SAS). In-plane magnetic fields change the energy diagram of the double quantum point contact giving rise to new crossing and anticrossing states. For the weak coupling device with an AlAs barrier, we find an intriguing reduction of the height of the conductance steps due to the imperfect coupling between ID subbands and the two-dimensional reservoir. This allows us to quantitatively estimate the coupling. (C) 2001 Elsevier Science B.V. All rights reserved.