A. Shailos

Can Kondo-like behavior occur in open quantum dots?

We discuss the possibility that a Kondo effect may arise in transport through open quantum dots, in which isolated periodic orbits, accessed by non-classical phase-space tunneling, serve as the localized charge that gives rise to the Kondo behavior. Some support for these ideas is shown to be provided by a simple formulation of the Anderson model, in which we assume the electron interaction strength within the dot to be strongly peaked at specific energies. Using this model, we are able to demonstrate behavior reminiscent of the metal-insulator transition, observed in our experimental studies of open quantum dots and dot arrays. The indication of these experiments appears to be that we enter a regime of many-body transport, which becomes effective once the temperature is lowered such that the discrete density of states of the dot becomes energetically resolved.

Localization, de-localization, phase breaking and energy relaxation in an array of quantum dots

We have studied both the phase-relaxation time and the energy-relaxation time in arrays of quantum dots. The variations of phase-breaking time with respect to temperature and current were related, suggesting a common electron temperature dependence, although these times differ by several orders of magnitude.

Variation of the temperature dependence of the energy-relaxation time with magnetic field in open quantum dot arrays at low temperatures

The variation of the magnetoconductance of two quantum dot arrays fabricated on GaAs/AlGaAs with temperature and sample current was used to extract carrier heating values at various magnetic fields. These measurements yielded a power law dependence of the electron temperature with the sample current and we study its variation with magnetic field. The power law exponent for the energy-relaxation time for both the dot arrays stays nearly constant over the entire magnetic field range.

Magnetic-field-driven transitions of chaotic dynamics in quantum cavities

The influence of a magnetic field on the classical dynamics in ballistic cavities is investigated by analyzing conductance fluctuations that result from quantum interference effects. The magnetic field transforms the exponential decay of the probability distributions of the dwell time and the enclosed area to a power-law decay. The conductance fluctuations correspondingly exhibit a transition from a nonfractal to a fractal behavior. We also identify two additional states that take place when the magnetic field is weaker or stronger than that required to achieve the power-law probability distributions.

Quantum-coherent transport in coupled quantum-dots

The details of electron interference in quantum-dot systems coupled via quantum point contacts (QPCs) is studied via simulation and experiment. In both open and closed coupled systems, one sees transitions from multi- to single-dot behavior, even when the QPCs support several modes. The results also reveal a non-trivial scaling of the conductance fluctuations in quantum-dot arrays, arising from the influence of the inter-dot coupling on energy hybridization.

Non-weak-localization signature in the average conductance of open quantum-dot arrays

Abstract The gate-voltage averaged conductance of open quantum-dot arrays is found to reveal the presence of a quantum correction that is quite inconsistent with the effects of weak localization. Our studies provide strong evidence for a greatly suppressed weak localization effect in these structures, which finding appears to be consistent with the results of our previous numerical investigations of these structures.

Magneto‐Conductance Oscillations in Open Quantum Dot Arrays

We study the influence of coherent inter-dot coupling on the transport properties of quantum dot arrays. The magneto-conductance oscillations observed in these open devices show a marked reduction in amplitude, and an associated suppression of their high frequency content, as we reduce the strength of the inter-dot coupling. We discuss these observations in the context of a transition from molecular- to atomic-like interference, which is induced as we suppress the strength of the inter-dot coupling.