Quantum Interference and Correlations in Electronic Transport Through Nanodevices

Abstract

Coherent electronic transport in nanostructures with strong electronelectron correlations has recently became a topic of broad interest, as it is fundamental to applications in quantum computing. The theoretical speed of quantum computers follows from the fact that they exploit the coherent superposition of wavefunctions. Coherence is achieved if the system size becomes smaller than the coherence length. In this case the typical quantum phenomena like interference or quantum many body effects as e.g. formation of many body resonances are observed. Quantum dot (QD) devices provide a well-controlled objects for studying these phenomena, as they offer the possibility of continuous tuning of the relevant parameters (see for example [1]). The gate voltage controls the number of the electrons at the dot and shifts the energy spectrum. Recent advances in technology allows to produce the QDs with tunable coupling between the electrodes and the dot. The energy spectrum of confined states of a nanostructure is discrete. A charging energy is, however, larger and Coulomb interactions are more important. Correlations between electrons lead to the Kondo resonance, which can be seen in transport through the QD [2]. Due to a specific quantum dot geometry the Kondo effect causes an enhancement of the conductance — in contrast to ”classical” magnetic impurities in metals, where the resistance increases [3]. There are many experimental evidences of quantum interference and strong correlation effects in coherent transport through quantum dots [1, 2] as well as in carbon nanotubes [4].