We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.

Josephson-junction arrays are ideal model systems to study a variety of phenomena such as phase transitions, frustration effects, vortex dynamics and chaos. In this review, we focus on the quantum dynamical properties of lowcapacitance Josephson-junction arrays. The two characteristic energy scales in these systems are the Josephson energy, associated with the tunneling of Cooper pairs between neighboring islands, and the charging energy, which is the energy needed to add an extra electron charge to a neutral island. The phenomena described in this review stem from the competition between single-electron effects with the Josephson effect. They give rise to (quantum) Superconductor-Insulator phase transitions that occur when the ratio between the coupling constants is varied or when the external fields are varied. We describe the dependence of the various control parameters on the phase diagram and the transport properties close to the quantum critical points. On the superconducting side of the transition, vortices are the topological excitations. In low-capacitance junction arrays these vortices behave as massive particles that exhibit quantum behavior. We review the various quantum-vortex experiments and theoretical treatments of their quantum dynamics.

The magnetoconductance of an open carbon nanotube ͑CNT͒-quantum wire was measured in pulsed magnetic fields. At low temperatures, we find a peculiar split magnetoconductance peak close to the chargeneutrality point. Our analysis of the data reveals that this splitting is intimately connected to the spin-orbit interaction and the tube chirality. Band-structure calculations suggest that the current in the peak regions is highly spin polarized, which calls for application in future CNT-based spintronic devices. DOI: 10.1103/PhysRevB.82.041404 PACS number͑s͒: 73.63.Fg, 75.47.Ϫm, 73.23.Ad, 85.75.Ϫd An efficient source of spin-polarized electrons is one of the important building blocks of a future spin-based electronics.1 Very high degrees of polarization can potentially be achieved by exploiting spin-orbit interaction ͑SOI͒. 2,3 Based on the low atomic number Z = 6 of carbon, the spin-orbit interaction in carbon nanotubes ͑CNTs͒ was mostly believed to be very weak, until a recent experiment 4 has demonstrated the effect of spin-orbit interaction in clean CNT quantum dots.In this Rapid Communication, we present magnetoconductance ͑MC͒ data for the complementary situation of an open CNT-quantum wire obtained in pulsed magnetic fields. Open quantum wires allow much higher currents ͑up to microampere͒ since a whole band participates in the transport rather than the individual levels in the quantum-dot regime. In a parallel magnetic field B ʈ , a small band-gap CNT evolves via a metallic state into a semiconducting one, resulting in a typical peak in the MC. 5,6 In one of our tubes, however, we observed a splitting of this MC peak into two peaks at low temperature. Recording MC traces at different gate voltage V g shows that the splitting vanishes when moving away from the charge-neutrality point ͑CNP͒. A thorough comparison to band-structure calculations reveals that the splitting is explained by the SOI, which becomes strong for small tube diameters. Our analysis predicts a highly spinpolarized current in the peak regions.The experiments have been performed on devices made of individual CNTs prepared on Si/ SiO 2 / Si 3 N 4 substrates. The heavily p-doped Si was used as a backgate and the thickness of the insulating layer was 350 nm. CNTs were grown by means of a chemical vapor deposition method 7 and Pd ͑50 nm͒ electrodes were defined on top of the tubes by e-beam lithography. In order to exclude strain effects on the band structure, 8 only straight and long ͑ϳ50 m͒ CNTs were selected for devices and the distance between two Pd electrodes was ϳ500 nm. The dc magnetoconductance was studied in pulsed magnetic fields of up to 60 T, applied parallel to the tube axis. The accuracy of the alignment was ϳ Ϯ 5°͑see supplementary material for further experimental details͒.9 Figure 1͑a͒ shows the magnetoconductance G͑B ʈ ͒ of a small-band-gap CNT device located near the CNP ͑diameter d ϳ 1.5 nm͒. At 82 K, the conductance G of the tube initially increases to reach a maximum at B 0 = 5.9 T, then it exponentially drops to zero ...

Cruciform-like molecules with two orthogonally placed π-conjugated systems have in recent years attracted significant interest for their potential use as molecular wires in molecular electronics. Here we present synthetic protocols for a large selection of cruciform molecules based on oligo(phenyleneethynylene) (OPE) and tetrathiafulvalene (TTF) scaffolds, end-capped with acetyl-protected thiolates as electrode anchoring groups. The molecules were subjected to a comprehensive study of their conducting properties as well as their photophysical and electrochemical properties in solution. The complex nature of the molecules and their possible binding in different configurations in junctions called for different techniques of conductance measurements: (1) conducting-probe atomic force microscopy (CP-AFM) measurements on self-assembled monolayers (SAMs), (2) mechanically controlled break-junction (MCBJ) measurements, and (3) scanning tunneling microscopy break-junction (STM-BJ) measurements. The CP-AFM measurements showed structure-property relationships from SAMs of series of OPE3 and OPE5 cruciform molecules; the conductance of the SAM increased with the number of dithiafulvene (DTF) units (0, 1, 2) along the wire, and it increased when substituting two arylethynyl end groups of the OPE3 backbone with two DTF units. The MCBJ and STM-BJ studies on single molecules both showed that DTFs decreased the junction formation probability, but, in contrast, no significant influence on the single-molecule conductance was observed. We suggest that the origins of the difference between SAM and single-molecule measurements lie in the nature of the molecule-electrode interface as well as in effects arising from molecular packing in the SAMs. This comprehensive study shows that for complex molecules care should be taken when directly comparing single-molecule measurements and measurements of SAMs and solid-state devices thereof.