Title 
Electronic transmittance phase extracted from mesoscopic interferometers


Published in 
Nanoscale Research Letters, October 2012

DOI  10.1186/1556276x7568 
Pubmed ID  
Authors 
M Ţolea, V Moldoveanu, IV Dinu, B Tanatar 
Abstract 
: The usual experimental setup for measuring the wave function phase shift of electrons tunneling through a quantum dot (QD) embedded in a ring (i.e., the transmittance phase) is the socalled 'open' interferometer as first proposed by Schuster et al. in 1997, in which the electrons backscattered at source and the drain contacts are absorbed by additional leads in order to exclude multiple interference. While in this case one can conveniently use a simple twopath interference formula to extract the QD transmittance phase, the open interferometer has also a number of drawbacks, such as a reduced signal and some uncertainty regarding the effects of the extra leads. Here we present a meaningful theoretical study of the QD transmittance phase in 'closed' interferometers (i.e., connected only to source and drain leads). By putting together data from existing literature and giving some new proofs, we show both analytically and by numerical simulations that the existence of phase lapses between consecutive resonances of the 'bare' QD is related to the signs of the corresponding Fano parameters  of the QD + ring system. More precisely, if the Fano parameters have the same sign, the transmittance phase of the QD exhibits a Π lapse. Therefore, closed mesoscopic interferometers can be used to address the 'universal phase lapse' problem. Moreover, the data from already existing Fano interference experiments from Kobayashi et al. in 2003 can be used to infer the phase lapses. 
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