The Kondo Effect in a Single-Electron Transistor
In our single electron transistor (SET), a droplet of about 50 electrons is separated from two conducting leads by tunnel barriers. A set of electrodes (Fig. 1(a)), on the surface of a GaAs/AlGaAs heterostructure which contains a two-dimensional electron gas (2DEG), is used to confine the electrons and create the tunnel barriers. The 2DEG is depleted beneath the electrodes, and the narrow constrictions between electrodes form the tunnel barriers. To make our SETs smaller than earlier ones, we have fabricated shallower 2DEG heterostructures  as well as finer metallic gate patterns by electron-beam lithography. The smaller size of the SETs is critical to our observation of the Kondo effect (dimensions are given in Fig. 1(a)). For details of device fabrication see Ref. .
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