Magnetic Coupling and Single-Ion Anisotropy in Surface-Supported Mn-based Metal-Organic Networks

The electronic and magnetic properties of Mn coordinated to 1,2,4,5-tetracyanobenzene (TCNB) in the Mn-TCNB 2D metal-ligand networks have been investigated by combining scanning tunneling microscopy and X-ray magnetic circular dichroism (XMCD) performed at low temperature (3 K). When formed on Au(111) and Ag(111) substrates the Mn-TCNB networks display similar geometric structures. Magnetization curves reveal ferromagnetic (FM) coupling of the Mn sites with similar single-ion anisotropy energies, but different coupling constants. Low-temperature XMCD spectra show that the local environment of the Mn centers differs appreciably for the two substrates. Multiplet structure calculations were used to derive the corresponding ligand field parameters confirming an in-plane uniaxial anisotropy. The observed interatomic coupling is discussed in terms of superexchange as well as substrate-mediated magnetic interactions.Comment: J. Phys. Chem. C 201

Micrometre-long covalent organic fibres by photoinitiated chain-growth radical polymerization on an alkali-halide surface

On-surface polymerization is a promising technique to prepare organic functional nanomaterials that are challenging to synthesize in solution, but it is typically used on metal substrates, which play a catalytic role. Previous examples on insulating surfaces have involved intermediate self-assembled structures, which face high barriers to diffusion, or annealing to higher temperatures, which generally causes rapid dewetting and desorption of the monomers. Here we report the photoinitiated radical polymerization, initiated from a two-dimensional gas phase, of a dimaleimide monomer on an insulating KCl surface. Polymer fibres up to 1 μm long are formed through chain-like rather than step-like growth. Interactions between potassium cations and the dimaleimide’s oxygen atoms facilitate the propagation of the polymer fibres along a preferred axis of the substrate over long distances. Density functional theory calculations, non-contact atomic force microscopy imaging and manipulations at room temperature were used to explore the initiation and propagation processes, as well as the structure and stability of the resulting one-dimensional polymer fibres

How Deep the Theory of Quantum Communications Goes: Superadditivity, Superactivation and Causal Activation

In the theory of quantum communications, a deeper structure has been recently unveiled, showing that the capacity does not completely characterize the channel ability to transmit information due to phenomena - namely, superadditivity, superactivation and causal activation - with no counterpart in the classical world. Although how deep goes this structure is yet to be fully uncovered, it is crucial for the communication engineering community to own the implications of these phenomena for understanding and deriving the fundamental limits of communications. Hence, the aim of this treatise is to shed light on these phenomena by providing the reader with an easy access and guide towards the relevant literature and the prominent results from a communication engineering perspective

From the Environment-Assisted Paradigm to the Quantum Switch

The quantum switch has been witnessing growing attention in the last years due to its advantage in several quantum technologies applications. In particular, it has been proven that the quantum switch can significantly improve the communication rates beyond the limits of conventional quantum Shannon theory. In this paper, we theoretically prove that the quantum switch can be interpreted as a particular instance of the Environment-assisted quantum communication paradigm. The developed analysis is crucial to better understand the limitations of the quantum switch. Furthermore, the analysis is key to shed the light on control strategies within the Environment-assisted communication paradigm

Quantum Internet: from Medium Access Control to Entanglement Access Control

Multipartite entanglement plays a crucial role for the design of the Quantum Internet, due to its potentiality of significantly increasing the network performance. In this paper, we design an entanglement access control protocol for multipartite state, which exhibits several attractive features. Specifically, the designed protocol is able to jointly extract in a distributed way an EPR pair from the original multipartite entangled state shared by the set of network nodes, and to univocally determines the identities of the transmitter node and the receiver node in charge of using the extracted EPR pair. Furthermore, the protocol avoids to delegate the signaling arising with entanglement access control to the classical network, with the exception of the unavoidable classical communications needed for EPR extraction and qubit teleportation. Finally, the protocol supports the anonymity of the entanglement accessing nodes

On-Surface Synthesis of Phthalocyanine Compounds

International Workshop on On-Surface Synthesis, FRANCE, MAY 25-30, 2014International audienceIn this chapter, we review the recent progress in the synthesis of phthalocyanine compounds at metallic surfaces under ultra-high vacuum conditions. Starting with tetra-carbonitrile-benzene molecules and magnetic atoms such as iron and manganese, we show that metal-organic coordination networks are formed at room temperature; then annealing at 500-600 K leads to the on-surface formation of phthalocyanine compounds. This reaction has been studied step-by-step by scanning tunneling microscopy and spectroscopy. The last part of this chapter is dedicated to the study of larger precursors functionalized with tetra-carbonitrile groups that react with copper atoms to form original polymers linked by phthalocyanine cores

Detection of somaclonal variation by random amplified polymorphic DNA analysis during micropropagation of Phalaenopsis bellina (Rchb.f.) Christenson

Phalaenopsis bellina (Rchb.f.) Christenson orchid species are known for their beautiful flower shape, graceful inflorescence and fragrance. Protocorm-like bodies (PLBs) of P. bellina were induced from leaf segments. The PLBs were then subjected to proliferation using ½ strength Murashige and Skoog (MS) media with two subcultures at three months intervals. Twelve decamer random amplified polymorphic DNA (RAPD) primers were used to study somaclonal variation among the mother plant, the initially induced PLBs and proliferated PLBs after 3 and 6 months in culture. Eight out of twelve primers produced 172 bands with 18 polymorphic bands in all the treatments. The amplified products varied between 125 to 8000 bp. Among the primers used, P 16 produced the highest number of bands (29), while primer OPU 10 produced the lowest number (15). The range of similarity coefficient was from 0.83 to 1.0 among the different sub-cultures and mother plant (MP). It was found that minimal or no changes occurred between the MP and the PLBs produced after 3 months of induction. The induced PLBs were then subcultured for six months for proliferation and this resulted in about 17% dissimilarity with MP. It is reported that micropropagation of P. bellina can be carried out successfully using ½ strength MS media for 6 months but further proliferation may result in somaclonal variation which might change the prolific characteristic of this orchids

Self-organised growth of molecular arrays at surfaces

International audienceThe autonomous ordering and assembly of atoms and molecules on atomically well-defined surfaces allow creating a wide range of surface nanostructures, opening an alternative 'bottom-up' route to the traditional 'top-down' fabrication methods of the microelectronics industry now approaching their fundamental limits. This review summarises some recent efforts of our team to grow molecular arrays on metal, insulating or semiconductor surfaces. In a fundamental approach, two-dimensional surface arrays of nanometre size have been obtained under ultrahigh vacuum by evaporation of molecules, functionalised to favour the intermolecular links rather than molecule-substrate ones. Intermolecular links such as hydrogen bonds, covalent or coordination bonding were profitably used to create various molecular networks. Alternatively, we also investigated molecular self-assembly from the solution whose architectures are mainly fixed by the molecule-substrate adsorption forces. Molecular assemblies were characterised using Scanning Near-Field Microscopies (Scanning Tunnelling Microscopy, non-contact-Atomic Force Microscopy), whereas electronic and vibrational properties were investigated by surface spectroscopy such as Ultra-Violet and X-ray Photoelectron Spectroscopy, infrared or Surface-Enhanced Raman Spectroscopy