Monday Evening Seminar

Monday, November 28, 2005

4:00 p.m.

107 Mason Lab

"Triple Quantum Dots"

Mr. Andy Vidan
Harvard Univsersity,
Div. of Engineering & Applied Sciences

Abstract

Following our work on a triple quantum dot single-electron rectifier, we report recent measurements on three quantum dots coupled in a ring geometry. The quantum dots are fabricated in a GaAs/AlGaAs heterostructure containing a two-dimensional electron gas using lithographically patterned gates and an etched trench in the center of the ring. By only energizing certain gates, this device allows us to study electron transport through a single dot, a double dot, or a triple dot ring. We can determine the absolute number of electrons in a quantum dot using a nearby charge sensor and find that we are able to tune a single dot to the one and two electron regime. We find several sharp peaks in the differential conductance, occurring at both zero and finite source-drain bias, for the one and two electron quantum dot. At zero source-drain bias, the temperature and magnetic field dependence of the conductance is consistent with a standard Kondo resonance. We attribute the peaks at finite-bias to a Kondo effect through excited states of the quantum dot.

Host: Jack Harris, Physics Department