Study on Within the Phase-Coherence Length |

ABSTRACT:

The results of the experiments mapping electron ow in a 2DEGshowed two surprising results. The _rst was the branched nature of the ow,explained as the eject of a disordered background potential. The second was theperseverance of regular interference fringes over the entire, several-micronrange of the scans. Interference fringes spaced by half of the Fermi wavelengthwere expected close to the point contact. At distances of several hundrednanometers, the various energies present in the electron own would remain inphase with one another. As one moves farther from the QPC, however, simpleconsiderations would suggest that the various frequencies would disperse andany interference e_ects would be washed out. The survival of the interferencefringes is seen in full quantum-mechanical simulations with thermal averaging,so we know that a complete theory will reproduce them. This full solution doesnot, however, tell us much about the mechanism that allows the fringes tosurvive. Inthis chapter, we begin by explaining why one might expect the fringes to die