The investigation of 1D and 2D phenomena using double-layer electron systems

The physics of low-dimensional electron systems continues to be an active field of research; using two examples we show how double-layer electron gases can extend these investigations. First, after reviewing the properties of 2D–2D tunnelling, we present equilibrium tunnelling measurements between a two-dimensional electron gas (2DEG) and an array of independent and identical 1D wires. Using a parallel magnetic field full information about the wires can be obtained, their 1D energies and wave functions, and hence the functional form of the confining potential. In the second case, the Coulomb drag (where a voltage is induced in one layer when a current is passed through the other) is measured between two separately contacted and electrically isolated 2DEGs. At temperatures comparable to the Fermi temperature, the measured transresistivity shows a plasmon enhancement. A comparison between theory and experiment shows the importance of many-body corrections to the coupled plasmon modes.