Creating a channel in a two-dimensional electron gas


Simulating the effect of two circular gates on a 2DEG: The lower surface represents the energy of the conductance band edge. The upper surface represents the Fermi energy. The energy of the conduction band edge is controlled by a gate voltage that is applied to a pair of circular gates that sit above the 2DEG. In a typical experiment, the gates would have other geometries. When the energy of the conduction band edge exceeds the Fermi energy, the electrons are drained out of that region of space. A channel is formed between the two gates. The channel gets narrower at large negative gate voltage, and then becomes closed. 


Persistent Current at Certain Magnetic Fields


Allowed momentum states in a metal ring: The animation shows the filled and unfilled states in a very small metal ring with a single transverse mode for electron transport. The magnetic flux threading the ring is varied from 0 to 1 flux quanta. The allowed values of k (the dynamic momentum of an electron going around the ring) change to accommodate the magnetic flux and still satisfy the periodic boundary condition. There are particular values of magnetic flux that maximize the net current circulating in the ring. 

Last modified: Wednesday, 29 September 2021, 10:40 AM