On the ballistic conductance of small contacts and its resonant structure: trumpet effect washes out resonant structure

Recent experimental results in 2D electron gas GaAs/GaAlAs structures seem to show that the ballistic electron conductance of small contacts, to a good approximation, is 'quantised (D. Wharam et al., 1988). Their present calculations for general geometries of the contacts which describe the experimental data reasonably well. The authors calculations show resonant scattering superimposed on the quantised conductance for some particular geometries. In general the resonances tend to be washed out and most probably in experimental geometries the resonances should not be present.