Tuning the confinement strength in a split-gate quantum wire

We present conductance measurements of a quantum wire defined by gating techniques which demonstrate independent control over the strength of the confinement potential and the carrier density. This is achieved by the introduction of a top gate over the standard split gates, so that the Fermi level in the wire can be adjusted without strongly affecting the confinement potential, permitting access to a wider range of transport régimes than is possible in conventional split-gate devices. In particular, the régime of weak confinement necessary for the formation of a ferromagnetic Wigner crystal predicted by Klironomos, Meyer and Matveev [Europhys. Lett. 74 (2006) 679] can be explored. Subband spectroscopy confirms our capability to control the strength of the confinement potential.