FRACTAL TRANSISTORS

We demonstrate a device which induces a controlled and reversible tran sition in the scattering dynamics of electrons, from nominally 'regula r' to 'chaotic' motion of the electrical current. This is achieved usi ng a gate-defined semiconductor cavity which undergoes an evolution in shape from a square to a 'Sinai' geometry. We report remarkable fract al behaviour which appears in the device conductance at low temperatur es during the transition. This is the first example of a man-made syst em where fractals can be introduced and removed in a controllable fash ion. Classical simulations are employed to determine the electron path s associated with conductance structure seen at the different scales.