Coherent transport through a ring of three quantum dots

Low field magnetotransport measurements have been performed on a ring of three few electrons quantum dots with well-defined electron occupations. In particular detailed measurements were made at two quadruple points (where four electronic configurations are degenerate) searching for an interplay between spin-blockade mechanisms and the Aharanov-Bohm effect. Measurements were also made at neighboring triple points. An analysis of the experimental magnetotransport fast Fourier transforms (FFTs) confirms coherent transport in our device. We find, however, transport features virtually independent of the particular quantum-dot configuration in the sense that the same periods and general behavior are observed in all of the FFTs. The two dominant frequencies in the FFTs were related by a factor 3. The origin of this fractional feature in the magnetoconductance behavior is not well understood. Other even higher frequency periods also exist. All magnetoconductance periods are found to be limited by phase rigidity, confirming that their origin lies within the quantum dot circuit itself.