Zigzag-Shaped Superlattices on the Basis of Graphene Nanoribbons: Structure and Electronic Properties

This is the author accepted manuscript. The final version is available from Springer Verlag via the DOI in this record.The paper focuses on superlattices consisting of two coplanar fragments of one-layer graphene nanoribbons that have different width and are connected at an angle. Classification of such superlattices was carried out; their electronic properties were studied using the tight-binding method. It was demonstrated that in superlattices consisting of two fragments of graphene nanoribbons with armchair edges connected at an angle of 60°, the band gap can be regulated by the number of dimeric carbon atom chains of one of the fragments. In that case one can observe a periodic dependence of the band gap on the number of chains with a characteristic period equal to three dimeric chains. The number of dimeric chains of the second superlattice fragment regulates the average band gap value near which the periodic oscillations occur, as well as the amplitude of those oscillations. Therefore, one can accomplish a sufficiently precise band gap tuning for such structures. Such tuning can find its wide application in the booming carbon nanoelectronics industry when creating generators, amplifiers and sensors in the nanochains.This research was supported by projects FP7 ITN NOTEDEV(FP7-607521), CACOMEL(FP7-247007), FAEMCAR (FP7-318617) and CANTOR (FP7-612285); project H2020-MSCA-RISE-2014 CoExAN (SEP-210156718); European Graphene Flagship project (604391), as well as by the Belarusian Ministry of Education (grant 20140773), Belarusian State University (grant 11, 2014), and the international grant AFOSR “Nanosized CherenkovType Terahertz Light Emitter Based on Double-Walled Carbon Nanotubes and Bi-graphene Nanoribbons”

Band gaps in jagged and straight graphene nanoribbons tunable by an external electric field.

PublishedJournal ArticleResearch Support, Non-U.S. Gov'tThis is the author accepted manuscript. The final version is available from IOP Publishing via the DOI in this record.Band gap control by an external field is useful in various optical, infrared and THz applications. However, widely tunable band gaps are still not practical due to a variety of reasons. Using the orthogonal tight-binding method for π-electrons, we have investigated the effect of the external electric field on a subclass of monolayer chevron-type graphene nanoribbons that can be referred to as jagged graphene nanoribbons. A classification of these ribbons was proposed and band gaps for applied fields up to the SiO2 breakdown strength (1 V nm(-1)) were calculated. According to the tight-binding model, band gap opening (or closing) takes place for some types of jagged graphene nanoribbons in the external electric field that lies on the plane of the structure and perpendicular to its longitudinal axis. Tunability of the band gap up to 0.6 eV is attainable for narrow ribbons. In the case of jagged ribbons with armchair edges larger jags forming a chevron pattern of the ribbon enhance the controllability of the band gap. For jagged ribbons with zigzag and armchair edges regions of linear and quadratic dependence of the band gap on the external electric field can be found that are useful in devices with controllable modulation of the band gap.Thisworkwas supported by EU FP7 ITNNOTEDEV (through Grant No. FP7-607521); IRSES projects CACOMEL (Grant No. FP7-247007), FAEMCAR (Grant No. FP7-318617) and CANTOR (Grant No. FP7-612285); Graphene Flagship (Grant No. 604391) and the Ministry of Education of the Republic of Belarus (Grant No. 20140773). The authors are very grateful to Prof P Lambin and Prof M Portnoi for their useful advice and Charles Downing for his careful reading of the manuscript

Quantum Rings in Electromagnetic Fields

This is the author accepted manuscript. The final version is available from Springer via the DOI in this recordThis chapter is devoted to optical properties of so-called Aharonov-Bohm quantum rings (quantum rings pierced by a magnetic flux resulting in AharonovBohm oscillations of their electronic spectra) in external electromagnetic fields. It studies two problems. The first problem deals with a single-electron AharonovBohm quantum ring pierced by a magnetic flux and subjected to an in-plane (lateral) electric field. We predict magneto-oscillations of the ring electric dipole moment. These oscillations are accompanied by periodic changes in the selection rules for inter-level optical transitions in the ring allowing control of polarization properties of the associated terahertz radiation. The second problem treats a single-mode microcavity with an embedded Aharonov-Bohm quantum ring which is pierced by a magnetic flux and subjected to a lateral electric field. We show that external electric and magnetic fields provide additional means of control of the emission spectrum of the system. In particular, when the magnetic flux through the quantum ring is equal to a half-integer number of the magnetic flux quanta, a small change in the lateral electric field allows for tuning of the energy levels of the quantum ring into resonance with the microcavity mode, thus providing an efficient way to control the quantum ring-microcavity coupling strength. Emission spectra of the system are discussed for several combinations of the applied magnetic and electric fields

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A device called a light well might form the basis of a tunable nanoscale laser