Coupling-driven transition from multiple to single-dot interference in open quantum-dot arrays

Abstract

The details of electron interference in open quantum-dot arrays are studied in experiment and numerical simulations. Reproducible fluctuations are observed in their low-temperature magnetoconductance and the characteristics of these are suggested to be consistent with a transition from multiple to single-dot interference, which occurs as the strength of the interdot coupling is varied. These results therefore reveal a nontrivial scaling of the conductance fluctuations in quantum-dot arrays, which is thought to arise due to the influence of the interdot coupling on energy hybridization.

Einselection and the quantum to classical transition in quantum dots

“…The pointer states apparently do not significantly decohere within one dot or the dot array, but this decoherence occurs within the environment as represented by this quasi-two-dimensional contact system. This is a very interesting result, and is in agreement with studies which have shown that the fluctuations themselves can be composed of orbits which are coherent across the dots of the array [45]. Indeed, there is some indication in figure 16, that the phase-breaking time is longer in the four dot array than in the three dot array.…”

Investigation of electron wave function hybridization in Ga0.25In0.75As/InP arrays

“…The Ga x In 1−x As material system is increasingly employed for studies of quantum transport phenomena, such as quantum coherence 9 and engineered conductance asymmetry, 4 rather than the traditional Al x Ga 1−x As/ GaAs heterostructures. 5,6 The reduced effective mass m ‫ء‬ of our Ga 0.25 In 0.75 As quantum well ͑with a measured m ‫ء‬ = 0.04m e compared to 0.067m e for GaAs͒ produces larger energy level spacings, making this system optimal for studies of energy level hybridization. Three separate arrays, comprising one, two, and three coupled dots, are defined within a twodimensional electron gas ͑2DEG͒ situated in the 9 nm wide quantum well.…”

“…Whereas the majority of previous coupling studies have focused on electron transport mediated by tunneling between "closed" quantum dots, [1][2][3] here we focus on the "open" transport regime where the devices are connected by conducting channels. [4][5][6] We will describe a measurement technique for quantifying the evolution of the quantum energy level spectrum of the open arrays as the coupling strength of the connecting channels is varied and the number of devices in the array, N dot , is increased. This technique employs magnetoconductance fluctuations ͑MCF͒ to probe the decrease in the average spacing of the quantum energy levels as the electron wave functions undergo hybridization.…”

Magnetoconductance switching in an array of oval quantum dots

“…At higher magnetic field strengths the quantum Hall effect sets in, accounting for a steplike varying magnetoconductance, formation of edge states and characteristic multichannel fluctuations in the transmission spectra 27,28,29 . Localization effects and conductance fluctuations manifest themselves in a large variety of open quantum dot systems, regardless of whether ballistic 12,19,20,30,31,32 or diffusive 32,33,34,35 transport is considered. Assembling in-dividual dots into coupled arrays or lattices gives rise to new features of the system's overall response, depending on the type and strength of coupling 25,36,37,38,39,40 .…”

“…Assembling in-dividual dots into coupled arrays or lattices gives rise to new features of the system's overall response, depending on the type and strength of coupling 25,36,37,38,39,40 . Of particular interest are systems where the interplay between the various effects of electron transport mentioned above can be used to achieve a tunable quantum conductance, in terms of designing the size, shape and material specific features of the conducting device, as well as varying macroscopically accessible parameters such as externally applied fields, temperature, and gate voltages controlling the coupling strength between constituents 11,15,25,35,40,41,42 .…”