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Population switching and charge sensing in quantum dots: A case for quantum phase transitions

Categories: Physics - Condensed Matter (PHYS-CM)
Speaker: Moshe Goldstein, (Bar-Ilan)
Date & Time: October 26, 2009 - 1:30pm
Location: Serin Physics 385

``Population switching'' is a phenomenon involving a steep filling of a narrow level in a quantum dot at the expense of a wide one as a common gate voltage is varied. This effect has been discussed in several contexts, including charge sensing by means of a current-carrying quantum point contact (QPC), as well as in relation with lapses of the transmission phase of a quantum dot. Is the switching involved abrupt, in which case one is facing a first order quantum phase transition? Mapping this problem onto a two-species Coulomb gas representation, we demonstrate that it is equivalent to an orbital Kondo model, and find that the switching is steep but not abrupt; however, when one tries to measure this behavior by electrostatically coupling one of the levels to a charge detecting QPC, one may render the switching abrupt. We show that this quantum phase transition is triggered by a change in physics from a Mahan exciton controlled dynamics to an Anderson orthogonality catastrophe controlled dynamics.  Including the spin degree of freedom may lead to a realization of the SU(4) Kondo effect, as well as to quantum criticality of the two-impurity-Kondo type.

Advancing Nanotechnology - IAMDN New Microscopes


Rutgers new scanning transmission electron microscope and new helium ion microscope help researchers develop nanotechnology used to fight cancer, generate power, and create more powerful electronics. Watch the video to learn more.

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