NER: Enhanced Magnetoabsorption Oscillations in Semiconductor Nanorings

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This is a Nanoscale Exploratory Research (NER) award that is funded as a result of a proposal submitted to the Nanoscience and Engineering (NSE) initiative. This theoretical research focuses on new phenomena and the resulting functionalities that may be afforded by intrinsic ring-shaped semiconductor nanostructures, called nanorings, based on recently developed fabrication capabilities. In preliminary work, we have predicted that nanorings should exhibit sensitive magneto-optical characteristics in the presence of a static or high-frequency electric field as a magnetic flux threading an intrinsic nanoring is varied. Spectroscopic signatures associated with magnetic field changes of ~0.1 Tesla are evident in the presence of dc electric fields on the order of 1-10kV/cm (consistent with ~1 V potential applied across the structure). The magnetic-field sensitivity is considerably superior to that typically associated with magnetoexcitons in quantum wells where magnetic fields in excess of one Tesla is often needed to affect an appreciable spectroscopic change. Moreover, unlike the analogous transport phenomena, these magneto-optical phenomena are predicted to occur at temperatures up to several tens of Kelvins.This provides a potentially sensitive optical probe of the Aharonov-Bohm effect of neutral excitons in nanorings, in which the magnetoabsorption varies periodically with the threading flux, the period being given by the electron flux quantum hc/e. The demonstration - both theoretical and experimental - of the Aharonov-Bohm effect in the optical properties of semiconductor nanorings, moreover, spurs the search for related phenomena that have traditionally been in the domain of transport. We have begun work investigating the effects of disorder, with an eye on possible Al'tschuler-Aronov-Spivak oscillations, whose period hc/2e is half the electron flux quantum. In addition, effects analogous to universal conductance fluctuations are likely to be observable in the frequency vicinity of an excitonic resonance. Such optical studies allow for superior frequency and wavevector selectivity compared with transport measurements where there is limited control of these parameters.The studies will determine the feasibility of devices exploiting this effect and provide a theoretical basis for related problems. This research is both of fundamental and applied interest across several fields of physics and engineering. The work will be carried out in collaboration with groups in Germany and Switzerland, in addition to Georgia Tech.%%%This is a Nanoscale Exploratory Research (NER) award that is funded as a result of a proposal submitted to the Nanoscience and Engineering (NSE) initiative. This theoretical research focuses on new phenomena and the resulting functionalities that may be afforded by intrinsic ring-shaped semiconductor nanostructures, called nanorings, based on recently developed fabrication capabilities. In preliminary work, we have predicted that nanorings should exhibit sensitive magneto-optical characteristics in the presence of a static or high-frequency electric field as a magnetic flux threading an intrinsic nanoring is varied. The studies will determine the feasibility of devices exploiting this effect and provide a theoretical basis for related problems. This research is both of fundamental and applied interest across several fields of physics and engineering. The work will be carried out in collaboration with groups in Germany and Switzerland, in addition to Georgia Tech.***