Artificial Atoms

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9732579 Kastner The research suggested in this proposal concerns the properties of quantum dots and single electron transistors. The properties of these quantum dots ("artificial atoms") are sufficiently different from ordinary electronic devices to require fundamental studies with the long range goal of translating these novel structures into technologically mature systems. This requires determining the energy levels and transition probabilities for these artificial atoms whose diameters are typically 1000 times the size of ordinary atoms. Transistors based on the artificial atom principle, the "single electron transistors" (SET), are the goal of the next generation of electronic devices. The research proposed here focuses on two topics, namely 1) how do electrons in an artificial atom interact with those in nearby metallic leads and 2) what is the nature of the phase transitions of the electron droplets in high magnetic fields. The coupling of topic 1) is believed to be give rise to behaviors closely related to the Kondo effect, which results from the coupling of localized electrons on a magnetic impurity to the Fermi liquid in a host metal. The second topic relates to the magnetic field induced phase transition from a singlet state to the ferromagnetic state in droplets with many electrons. The Kondo problem will be investigated for SETs carrying various numbers of electrons. The phase transitions will be studied by measuring the magnetic susceptibilties for magnetic fields greater than the critical field of ca. 1.7 tesla. %%% Research suggested in this proposal deals with fundamental problems of the behavior of quantum dots, also called artificial atoms. Such systems have great potential to become nano-scale electronic components, including "single electron transistors" (SETs), which will become the heart of the next generation of practical electronic devices. The properties of quantum dots are so different from those of ordinary atoms that the fundamental physics governing their behavior is not yet fully understood. Such understanding will facilitate a more efficient and controlled manufacture of SETs and their incorporation in practical technological devices. Two problems are attacked in the research described in this proposal. Both of them deal with electric current flow into and out of the SETs via the leads made of ordinary metal. ***