WHERE IS THE POTENTIAL DROP IN A QUANTUM POINT-CONTACT

A scattering theory calculation is presented for the potential distrib ution and the associated current-voltage characteristic in a ballistic quantum point contact. Following Landauer's idea, the electric field is calculated as the response to a given incoming current. The field i s finite only near the entrance to or exit from the constriction, whil e no potential drop occurs in the device itself, where the motion is a diabatic. As a result dissipation is restricted to the reservoirs, who se detailed description, however, requires inelastic scattering. (C) 1 998 Academic Press Limited.