Imaging Electron Flow in Two-Dimensional Electron Gases

We present images of electron flow from a quantum point contact (QPC) into a surrounding two-dimensional electron gas (2DEG). We resolve flow patterns associated with the one-dimensional modes responsible for quantized conductance through the QPC. The imaging technique relies on scanning a charged tip over the 2DEG and simultaneously measuring the conductance through the sample [1]. We show images of electron flow in different GaAs/AlGaAs heterostructures, and we discuss which features of 2DEGs can affect both application of this technique and the observed current flow paths. [1] M. A. Topinka \textit{et al.}, Nature 410, 183 (2001).