Phase Measurements in Aharonov-Bohm Interferometers

Authors : Amnon AHARONY, Ora ENTINWOHLMAN, Yoseph IMRY

Pages : 299-312

Doi:10.3906/sag-1202-104

View : 18 | Download : 11

Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :In this paper we address measurements of the resonant quantum transmission amplitude tQD = -i|tQD|eiaQD through a quantum dot insert ignore into journalissuearticles values(QD);, as function of the plunger gate voltage V. Mesoscopic solid state Aharonov-Bohm interferometers insert ignore into journalissuearticles values(ABI); have been used to measure the ``intrinsic` phase, aQD, when the QD is placed on one of the paths. In a ``closed` interferometer, connected to two terminals, the electron current is conserved, and Onsager`s relations require that the conductance G through the ABI is an even function of the magnetic flux F = \hbar cf/e threading the ABI ring. Therefore, if one fits G to A+B \cosinsert ignore into journalissuearticles values(f+b); then b only ``jumps` between 0 and p, with no relation to aQD. Additional terminals open the ABI, break the Onsager relations and yield a non-trivial variation of b with V. After reviewing these topics, we use theoretical models to derive three results on this problem: insert ignore into journalissuearticles values(i); For the one-dimensional leads, the relation |tQD|2 \propto \sin2insert ignore into journalissuearticles values(aQD); allows a direct measurement of aQD. insert ignore into journalissuearticles values(ii); In many cases, the measured G in the closed ABI can be used to extract both |tQD| and aQD. insert ignore into journalissuearticles values(iii); For open ABI`s, b depends on the details of the opening. We present quantitative criteria insert ignore into journalissuearticles values(which can be tested experimentally); for b to be equal to the desired aQD: the ``lossy` channels near the QD should have both a small transmission and a small reflection.
Keywords : interference in nanostructures, Aharonov Bohm interferometer, quantum dots, resonant transmission