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Perylenediimide (PDI) compounds with no substituents in their core are widely used as the active units of thin-film organic lasers. Recently, bay-substituted PDIs (b-PDIs) bearing two sterically hindering diphenylphenoxy groups at the 1,7-bay positions have received great attention because they show red-shifted emission with respect to bay-unsubstituted PDIs, while maintaining high photoluminescence (PL) quantum yields and low amplified spontaneous emission (ASE) thresholds even at high doping rates. However, their ASE photostability is relatively low compared to that of state-of-the-art PDIs. Thus, the design of b-PDIs with improved ASE photostability remains a challenge. Here, the synthesis of two b-PDIs with phenyl-type substituents at the imide positions is reported. Complete characterization of their optical properties, including absorption, PL, ASE, and transient spectroscopy, supported also by quantum chemical calculations, is performed with the dyes diluted in either a liquid solvent or a polystyrene film. Film experiments were accomplished at very low doping rates, to resemble the isolated molecule behavior, and also in a range of increasing doping rates, to investigate concentration quenching effects. The reported b-PDIs show improved ASE photostability (3-fold) with respect to b-PDIs with aliphatic-type substituents at the imide positions, whilst they show more propensity toward aggregation. The authors thank the Spanish Ministry of Economy and Competitiveness MINECO and the European Social Funds (project MAT2015-66586-R and FPI fellowship BES-2016-077681), the Ministry of Science and Innovation (MICINN) and the European FEDER funds (CTQ2016-77039-R, PGC2018-099568-B-I00, and PID2019-109200GB-I00, and Unidad de Excelencia María de Maeztu CEX2019-000919-M), and the Generalitat Valenciana (PROMETEO/2020/077 and SEJI/2018/035). J.A. acknowledges the MICINN for the “Ramón-y-Cajal” Fellowship (RyC-2017-23500).

La litografía por haz de electrones ó técnica EBL es a día de hoy una interesante herramienta de trabajo en diversos campos de estudio e investigación de Ciencia de Materiales, gracias a su alto potencial para la nanofabricación de bajo coste, su rapidez de implementación y ofrecer al mismo tiempo la posibilidad de su uso sin necesidad de formación y conocimientos excesivamente profundos . Concretamente, este trabajo se ha centrado en poner en marcha la técnica de litografía en la Universidad de Alicante desde cero, aprendiendo los pasos involucrados en la creación de nanoelementos. A su vez, se han realizado unas primeras pruebas de conductividad sobre los resultados obtenidos una vez se ha completado el proceso de fabricación. La máquina utilizada consiste en un microscopio de barrido electrónico ó SEM adaptado para la litografía, que permite tanto la formación de imágenes de alta resolución como la puesta en práctica de dicha técnica. Si bien el microscopio adaptado es el eje central de este trabajo en particular y de la técnica EBL en general, todo el proceso de fabricación involucra otras técnicas experimentales de distintos ámbitos para una mayor sistematización del estudio. En este aspecto, nos hemos apoyado de los compañeros y profesores que nos han enseñado las técnicas y cuestiones prácticas que hemos ido necesitando durante el camino.

Here we report on the identification and characterization of suspended double-stranded Au atomic chains up to ∼4 atoms long, using a scanning tunneling microscope adapted for the fabrication and simultaneous recording of the conductance. These chains are one of the smallest structures with the highest stability connecting two metallic electrodes, identified from the evolution of the conductance in the process of the controlled breakage of the contact between two metals. Molecular dynamics simulations and density functional theory electron transport calculations help us to unveil the richness of the geometric structures appearing in the experiments in the form of double-stranded chains, their stability, and how these can evolve into the formation of monoatomic chains. This work was supported by the Generalitat Valenciana through PROMETEO2017/139, the Spanish government through Grants MAT2016-78625-C2-1-P, FIS2016-80434-P, and PID2019-109539GB-C4, and the Marı́a de Maeztu Programme for Units of Excellence in R&D (CEX2018-000805-M); by Comunidad Autónoma de Madrid through Grant S2018/NMT-4321 (NanomagCOST-CM), by the Fundación Ramón Areces, and by the European Union Graphene Flagship under Grant No. 604391. C.S. gratefully acknowledges financial support from Generalitat Valenciana with the programs GENT (CDEIGENT2018/028). J.J.P. acknowledges the computer resources and assistance provided by the Barcelona Supercomputing Center (FI-2019-2-0007) and the Universidad Autónoma de Madrid.

The spin and lattice dynamics of a ferromagnetic nanoparticle are studied via molecular dynamics and with semi-classical spin dynamics simulations where spin and lattice degrees of freedom are coupled via a dynamic uniaxial anisotropy term. We show that this model conserves total angular momentum, whereas spin and lattice angular momentum are not conserved. We carry out simulations of the Einstein–de Haas effect for a Fe nanocluster with more than 500 atoms that is free to rotate, using a modified version of the open-source spin-lattice dynamics code (SPILADY). We show that the rate of angular momentum transfer between spin and lattice is proportional to the strength of the magnetic anisotropy interaction. The addition of the anisotropy allows full spin-lattice relaxation to be achieved on previously reported timescales of ∼ 100 ps and for tight-binding magnetic anisotropy energies comparable to those of small Fe nanoclusters. We acknowledge financial support from the Ministry of Science and Innovation of Spain (grant No. PID2019-109539GB-4). This work was supported by the Generalitat Valenciana, Spain through PROMETEO2017/139 and PROMETEO/2021/017. C. S. gratefully acknowledges financial supports from Generalitat Valenciana with (CDEIGENT2018/028). JFR acknowledges funding from FCT, Portugal grant PTDC/FIS-MAC/2045/2021. The SLD calculations in this paper were performed on the high-performance computing facilities of the University of South Africa.

Zigzag edged nanographenes such as peri-acenoacenes are promising materials for organic lasers, but the effects of heteroatom doping on the electronic properties and gain medium performance remain unclear. Herein, the facile synthesis of a new 1,2-oxaborine (BO) doped peri-tetracenotetracene derivative, the bis(1,2-oxaborine)peri-tetracenotetracene (BOTT-Mes), is reported. X-ray crystallographic analysis confirms the BO-doped planar structure and the nonexistence of intermolecular π–π stacking in solid state. Compared with the all-carbon peri-tetracenotetracene derivative (TT-Ar), the BO-doped BOTT-Mes exhibits more disrupted π-conjugation at the BO sites, a lower-lying highest occupied molecular orbital, and a larger energy gap. Due to its rigid skeleton and nonaggregative feature, it displays well-resolved absorption and emission spectra with a small Stokes shift (8 nm) and high photoluminescence quantum yield (80%) when it is dispersed in a polystyrene (PS) thin film. Notably, 1,2-oxaborine doping improves the film amplified spontaneous emission (ASE) performance, with a lower ASE threshold (Eth-ASE = 66 µJ cm–2) as compared to the TT-Ar doped PS film (Eth-ASE = 100 µJ cm–2). Furthermore, a low threshold (22 µJ cm–2) solution-processed distributed feedback laser is fabricated, indicating the feasibility of using BOTT-Mes as gain medium for practical laser applications. J.W. acknowledges financial support from A*STAR Advanced Manufacturing and Engineering grant (A20E5c0089) and National Research Foundation Investigatorship Award (NRF-NRFI05-2019-0005). The group at the University of Alicante acknowledges financial support from the “Ministerio de Ciencia e Innovación” of Spain, European Regional Development Fund and European Social Funds (PID2019-106114GB-I00 and BES-2016-077681) and from the Conselleria de Innovación, Universidades y Sociedad Digital de la Comunidad Valenciana (Grant No. AICO/2021/093).

Perylene‐fused, aggregation‐free polycyclic aromatic hydrocarbons with partial zigzag periphery (ZY‐01, ZY‐02, and ZY‐03) were synthesized. X‐ray crystallographic analysis reveals that there is no intermolecular π–π stacking in any of the three molecules, and as a result, they show moderate‐to‐high photoluminescence quantum yield in both solution and in the solid state. They also display the characteristic absorption and emission spectra of perylene dyes. ZY‐01 and ZY‐02 with a nearly planar π‐conjugated skeleton exhibit amplified spontaneous emission (ASE) when dispersed in polystyrene thin films. Solution‐processed distributed feedback lasers have been fabricated using ZY‐01 and ZY‐02 as active gain materials, both showing narrow emission linewidth (

We study the emergence of magnetism and its interplay with structural properties in a two-dimensional molecular crystal of cyclacenes, using density functional theory (DFT). Isolated cyclacenes with an even number of fused benzenes host two unpaired electrons in two topological protected zero modes, at the top and bottom carbon rings that form the molecule. We show that, in the gas phase, electron repulsion promotes an open-shell singlet with strong intramolecular antiferromagnetic exchange. We consider a closed packing triangular lattice crystal phase and we find a strong dependence of the band structure and magnetic interactions on the rotation angle of the cyclacenes with respect to the crystal lattice vectors. The orientational ground state maximizes the intermolecular hybridization, yet local moments survive. Intermolecular exchange is computed to be antiferromagnetic, and DFT predicts a broken symmetry 120∘ spin phase reflecting the frustration of the intermolecular spin coupling. Thus, the cyclacene crystal realizes a bilayer of two antiferromagnetically coupled S = 1/2 triangular lattices. Our results provide a bottom-up route towards carbon based strongly correlated platforms in two dimensions. We acknowledge funding support from Ministry of Science and Innovation of Spain (Grants No. PID2019-106114GB-I00 and No. PID2019-109539GB), Generalitat Valenciana and Fondo Social Europeo (Grant No. ACIF/2018/175), Generalitat Valenciana (Grant No. Prometeo2017/139), and FEDER/Junta de Andalucía Consejería de Transformación Económica, Industria, Conocimiento y Universidades, Grant No. PY18-4834.

The Haldane phase for antiferromagnetic spin-1 chains is a celebrated topological state of matter, featuring gapped excitations and fractional spin-1/2 edge states. Here, we provide numerical evidence that this phase can be realized with a Hubbard model at half filling, where each $s=1$ spin is stored in a four-site fermionic structure. We find that the noninteracting limit of our proposed model describes a one-dimensional topological insulator, and we conjecture it to be adiabatically connected to the Haldane phase. Our work suggests a route to build spin-1 networks using Hubbard model quantum simulators., Revised version, including Supplemental Material

Paramagnons are the collective modes that govern the spin response of nearly magnetic conductors. In some cases they mediate electron pairing leading to superconductivity. This scenario may occur in 2H-NbSe$_2$ monolayers, that feature spin-valley coupling on account of spin-orbit interactions and their lack of inversion symmetry. Here we explore spin anisotropy of paramagnons both for non-centrosymmetric Kane-Mele-Hubbard models for 2H-NbSe$_2$ monolayers described with a DFT-derived tight-binding model. In the infinite wavelength limit we find spatially uniform paramagnons with energies around $1$~meV that feature a colossal off-plane uniaxial magnetic anisotropy, with quenched transversal spin response. At finite wave vectors, longitudinal and transverse channels reverse roles: XY fluctuations dominate within a significant portion of the Brillouin zone. Our results show that 2H-NbSe$_2$ is close to a Coulomb-driven in-plane (XY) spin density wave instability., Comment: 10 pages (6 main text, 4 supplementary material), 10 figures (4 in the main text, 6 in the SM)

A theorem that establishes a one-to-one relation between zero-temperature static spin-spin correlators and coupling constants for a general class of quantum spin Hamiltonians bilinear in the spin operators has been recently established by J. Quintanilla, using an argument in the spirit of the Hohenberg-Kohn theorem in density functional theory. Quintanilla's theorem gives a firm theoretical foundation to quantum spin Hamiltonian learning using spin structure factors as input data. Here we extend the validity of the theorem in two directions. First, following the same approach as Mermin, the proof is extended to the case of finite-temperature spin structure factors, thus ensuring that the application of this theorem to experimental data is sound. Second, we note that this theorem applies to all types of Hamiltonians expressed as sums of bilinear operators, so that it can also relate the density-density correlators to the Coulomb matrix elements for interacting electrons in the lowest Landau level., Comment: 4 pages

The interactions of the spins of single atoms with a substrate can be controlled via the moiré lattice created by depositing a 2D material on top of the substrate.

A naphtho[2,1-b:6,5-b′]difuran derivative was found to serve as an effective violet-emitting laser dye. It showed amplified spontaneous emission at 413 nm with the threshold of 1.1–2.9 mJ cm−2 using 0.1–0.5 wt% in polystyrene film. Lasing was also demonstrated using all-polymeric distributed-feedback lasers emitting at 411–417 nm with the threshold of 2.0–2.9 mJ cm−2. This work was supported by JSPS KAKENHI grant JP19H05716 (to H. T.) and by the “Ministerio de Ciencia, Innovación y Universidades” of Spain, via grants MAT2015-66586-R and PID2020-119124RB-I00 and by the “Generalitat Valenciana” through grant AICO/2021/093.

The molecule N,N′-bis(3-methylphenyl)-N,N′-dyphenylbenzidine (TPD) has been widely used in optoelectronic applications, mainly for its hole-transporting properties, but also for its capability to emit blue light and amplified spontaneous emission, which is important for the development of organic lasers. Here, we report deep-blue-emitting distributed feedback (DFB) lasers based on TPD dispersed in polystyrene (PS), as active media, and dichromated gelatin layers with holographically engraved relief gratings, as laser resonators. The effect of the device architecture (with the resonator located below or on top of the active layer) is investigated with a dye (TPD) that can be doped into PS at higher rates (up to 60 wt%), than with previously used dyes (&lt, 5 wt%). This has enabled changing the index contrast between film and resonator, which has an important effect on the laser performance. With regards to thresholds, both architectures behave similarly for TPD concentrations above 20 wt%, while for lower concentrations, top-layer resonator devices show lower values (around half). Remarkably, the operational durability of top-layer resonator devices is larger (in a factor of around 2), independently of the TPD concentration. This is a consequence of the protection offered by the resonator against dye photo-oxidation when the device is illuminated with pulsed UV light.

Fractionalization is a phenomenon in which strong interactions in a quantum system drive the emergence of excitations with quantum numbers that are absent in the building blocks. Outstanding examples are excitations with charge e/3 in the fractional quantum Hall effect, solitons in one-dimensional conducting polymers and Majorana states in topological superconductors. Fractionalization is also predicted to manifest itself in low-dimensional quantum magnets, such as one-dimensional antiferromagnetic S = 1 chains. The fundamental features of this system are gapped excitations in the bulk and, remarkably, S = 1/2 edge states at the chain termini, leading to a four-fold degenerate ground state that reflects the underlying symmetry-protected topological order. Here, we use on-surface synthesis to fabricate one-dimensional spin chains that contain the S = 1 polycyclic aromatic hydrocarbon triangulene as the building block. Using scanning tunneling microscopy and spectroscopy at 4.5 K, we probe length-dependent magnetic excitations at the atomic scale in both open-ended and cyclic spin chains, and directly observe gapped spin excitations and fractional edge states therein. Exact diagonalization calculations provide conclusive evidence that the spin chains are described by the S = 1 bilinear-biquadratic Hamiltonian in the Haldane symmetry-protected topological phase. Our results open a bottom-up approach to study strongly correlated quantum spin liquid phases in purely organic materials, with the potential for the realization of measurement-based quantum computation., 23 pages, 4 main figures and 7 extended data figures; supplementary information containing additional data is included

High-transparency polymers, called optical polymers (OPs), are used in many thin-film devices, for which the knowledge of film thickness (h) and refractive index (n) is generally required. Spectrophotometry is a cost-effective, simple and fast non-destructive method often used to determine these parameters simultaneously, but its application is limited to films where h > 500 nm. Here, a simple spectrophotometric method is reported to obtain simultaneously the n and h of a sub-micron OP film (down to values of a few tenths of a nm) from its transmission spectrum. The method is valid for any OP where the n dispersion curve follows a two-coefficient Cauchy function and complies with a certain equation involving n at two different wavelengths. Remarkably, such an equation is determined through the analysis of n data for a wide set of commercial OPs, and its general validity is demonstrated. Films of various OPs (pristine or doped with fluorescent compounds), typically used in applications such as thin-film organic lasers, are prepared, and n and h are simultaneously determined with the proposed procedure. The success of the method is confirmed with variable-angle spectroscopic ellipsometry. Spanish Ministry of Economy and Competitivity (MINECO) and European Community (FEDER) through grant no. MAT2015-66586-R.

We systematically investigate the relationships between structural and electronic effects of finite size zigzag or armchair carbon nanotubes of various diameters and lengths, starting from a molecular template of varying shape and diameter, i.e. cyclic oligoacene or oligophenacene molecules, and disclosing how adding layers and/or end-caps (i.e. hemifullerenes) can modify their (poly)radicaloid nature. We mostly used tight-binding and finite-temperature density-based methods, the former providing a simple but intuitive picture about their electronic structure, and the latter dealing effectively with strong correlation effects by relying on a fractional occupation number weighted electron density (ρFOD), with additional RAS-SF calculations backing up the latter results. We also explore how minor structural modifications of nanotube end-caps might influence the results, showing that topology, together with the chemical nature of the systems, is pivotal for the understanding of the electronic properties of these and other related systems. A. J. P. J. and J. C. S. G acknowledge the project CTQ2014-55073-P from the Spanish Government (MINECO/FEDER) and the project AICO/2018/175 from the Regional Government (GVA/FSE). J. F. R. acknowledges the projects MAT2016-78625 from the Spanish Government (MINECO/FEDER) and projects No. PTDC/FIS-NAN/4662/2014 and No. PTDC/FIS-NAN/3668/2014 from the Portuguese Government (Fundaçao para a Ciencia e Tecnologia). D. C. is thankful to projects IT588-13 (Eusko Jaurlaritza) and CTQ2016-80955 from the Spanish Government (MINECO/FEDER). M. E. S.-S. acknowledges CONACyT-México for a PhD fellowship (ref. 591700). R. O. C. acknowledges “Generalitat Valenciana” and “Fondo Social Europeo” for a PhD fellowship (ACIF/2018/198).

Los materiales compuestos constituyen un bloque temático importante en las asignaturas Sólidos Inorgánicos (Grado en Química) y Ciencia de los Materiales (Grado en Química y Grado en Física) impartidas en la Universidad de Alicante. En los últimos años, el profesorado responsable de dichas asignaturas ha constatado que los estudiantes presentan dificultades en la comprensión del temario relacionado con los materiales compuestos y sus propiedades mecánicas. Hasta el momento, el desarrollo de dichos conceptos se había visto limitado a clases teóricas ya que no había sido posible trabajar con materiales compuestos en el laboratorio por su laboriosa fabricación y elevado coste de adquisición. Estas dificultades han motivado el desarrollo del presente trabajo, cuyo objetivo es el de aumentar el aprendizaje del estudiantado mediante: i) la utilización de herramientas de impresión 3D para la fabricación rápida y de bajo coste de materiales compuestos, ii) la predicción de sus propiedades mecánicas por simulación, y iii) su caracterización mecánica en el laboratorio. La experiencia, de carácter principalmente virtual, se realizó con estudiantes voluntarios y su evaluación se llevó a cabo mediante cuestionarios y encuestas de satisfacción. Además de representar una alternativa a las prácticas de laboratorio convencionales que requieren elevada presencialidad en épocas de pandemia, la experiencia ha fomentado el aprendizaje de los estudiantes.

The search of compounds emitting in the near-infrared (NIR) has been accelerated owing to their use in biomedical and telecommunications applications. In this regard, nanographenes (NGs) are attractive materials adequate for integration with other technologies, which have recently demonstrated amplified spontaneous emission (ASE) and lasing across the visible spectrum. Here, the optical and ASE properties of four-zigzag edged NGs of the [m,n]peri-acenoacene family are reported, whose size is increased through conjugation extension by varying n (from 3 to 5) while keeping m = 2. Results show that such 1D conjugation extension method is more efficient in terms of shifting the photoluminescence (PL) to the infrared (PL at 710 nm in the larger compound, PP-Ar) than through 2D conjugation extension as in previously reported NGs (PL at 676 nm with the largest compound FZ3, with n = 3 and m = 4). Additionally, PP-Ar shows dual-ASE (at 726 and 787 nm), whose origin is elucidated through Raman and transient absorption spectroscopies. These compounds’ potential for red and NIR lasing is demonstrated through the fabrication of distributed feedback lasers with top-layer resonators. This study paves the way towards the development of stable low-cost all-plastic NIR lasers. The authors acknowledge financial support from the “Ministerio de Ciencia, Innovación y Universidades” of Spain, European Regional Development Fund and European Social Funds (MAT2015-66586-R, PDI2019-106114GB-I00, BES-2016-077681, PGC2018-098533-B-100 and RED2018-102815-T). J.C. thanks the Junta de Andalucía of Spain (UMA18FEDERJA057). The authors also thank the Research Central Services (SCAI) of the University of Málaga. F.G. acknowledges the Spanish Government for an FPI grant. G.M.P. thanks Fondazione Cariplo (grant no 2018-0979) for the financial support. J.W. acknowledges the “Agency for Science, Technology and Research of Singapore” for financial support from A*STAR AME grant (A20E5c0089). A.M.R. and F.S. have received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. [816313]).

We study spin excitations and Kondo effect in open-shell nanographenes, motivated by recent scanning tunneling inelastic spectroscopy experiments. Specifically, we consider three systems, the triangulene, the extended triangulene with rocket shape, both with an $S=1$ ground state, and a triangulene dimer with $S=0$ on account of intermolecular exchange. We focus on the consequences of hybridization of the nanographene zero-modes with a conducting substrate on the $dI/dV$ lineshapes associated with spin excitations. The partially filled nanographene zero-modes coupled to the conduction electrons in the substrate constitute multi-orbital Anderson impurity models that we solve in the one-crossing approximation which treats the coupling to the substrate to infinite order. We find that the coupling to the substrate leads to (i) renormalization of the spin flip excitation energies of the bare molecule, (ii) broadening of the spectral features and (iii) the emergence of zero bias Kondo peaks for the $S=1$ ground states. The calculated substrate induced shift of the spin excitation energies is found to be significantly larger than their broadening, which implies that this effect has to be considered when comparing experimental results and theory., Comment: 9 pages, 4 figures; replaced with revised version, accepted in Phys. Rev. B

Van der Waals materials with narrow energy gaps and efficient response over a broadband optical spectral range are key to widen the energy window of nanoscale optoelectronic devices. Here, we characterize FePS as an appealing narrow-gap p-type semiconductor with an efficient broadband photo-response, a high refractive index, and a remarkable resilience against air and light exposure. To enable fast prototyping, we provide a straightforward guideline to determine the thickness of few-layered FePS nanosheets extracted from the optical transmission characteristics of several flakes. The analysis of the electrical photo-response of FePS devices as a function of the excitation energy confirms a narrow gap suitable for near IR detection (1.23 eV) and, more interestingly, reveals a broad spectral responsivity up to the ultraviolet region. The experimental estimate for the gap energy is corroborated by ab-initio calculations. An analysis of photocurrent as a function of gate voltage and incident power reveals a photo-response dominated by photogating effects. Finally, aging studies of FePS nanosheets under ambient conditions show a limited reactivity of the outermost layers of flakes in long exposures to air., The present work has received funding from the European Union’s Horizon 2020 research and innovation program through the European Research Council grants ERC-2017-StG-755655 2D-TOPSENSE, ERC-2018-AdG-788222 MOL-2D, under the Graphene Flagship through projects GrapheneCore2 (grant nr. 785219), and GrapheneCore3 (grant nr. 881603) and through the COST Action CA15128 MOLSPIN. The authors also acknowledge funding from the Spanish Government through the Unit of Excellence “María de Maeztu” MDM-2015-0538, through projects MAT2017- 88377-C2-2-R (AEI/FEDER), MAT2017-88377, MAT2017-89528 (AEI/FEDER), and R.F.’sJuan de la Cierva-formación fellowship FJCI-2017-32919. This work has been supported by the Generalitat Valenciana, through grants CIDEGENT/2018/004, CIDEGENT/2018/005, CDEIGENT/2019/022, the Prometeo Program of Excellence, and M.R.’s APOSTD/2020/249 fellowship.

En esta tesis exploramos las posibilidades que ofrecen sistemas basados en grafeno como soporte para tecnologías cuánticas. En particular estudiamos en profundidad las bicapas de grafeno en las que se depositan átomos de hidrógeno. Este tipo de defectos crean momentos magnéticos electrónicos localizados alrededor de los adátomos. Los adátomos de hidrógeno proporcionan a su vez el momento magnético nuclear del protón de su núcleo que interacciona con los momentos magnéticos electrónicos. El Hamiltoniano efectivo de este sistema comprende una multitud de términos que, cuando se combinan adecuadamente, pueden dar lugar a fases tanto débil como fuertemente correlacionadas. Las interacciones de Hamiltoniano efectivo pueden ser controladas a través de dos mecanismos. El primero, la ubicación de los defectos introducidos que puede ser elegida con precisión atómica usando STM. El segundo se basa en la apertura controlada de un gap en la estructura de bandas de las bicapas de localización/descolocación de los estados electrónicos depende fuertemente de la cercanía en energía de estados localizados, por lo que la apertura de un gap permite controlar la extensión de los electrones y su interacción con los defectos. Esta plataforma permitiría realizar experimentalmente un gran número de Hamiltonianos que a día de hoy carecen de realización experimental eligiendo la combinación correcta de parámetros entre los defectos y campo eléctrico (o lo que es lo mismo, extensión de los estados electrónicos).

Las dificultades en la comprensión de los conceptos necesarios para la correcta interpretación de la relación estructura-propiedades en los materiales compuestos en estudiantes de las asignaturas de “Sólidos Inorgánicos” (2º curso del Grado en Química), “Ciencia de los Materiales” (4º curso del Grado en Química) y “Ciencia de Materiales” (4º curso del Grado en Física) de la Universidad de Alicante, han supuesto el foco de atención para los participantes del presente proyecto. En la red INTERMAT X (red de investigación INTERdisciplinar en MATeriales), se evaluó la posibilidad de incorporar dichos conceptos, hasta ahora impartidos únicamente en clases teóricas, a la enseñanza experimental mediante el diseño y puesta en marcha de unas prácticas de laboratorio. En estas se plantea la utilización de la tecnología de impresión 3D para la fabricación y caracterización mecánica de materiales compuestos junto con la simulación computacional como apoyo conceptual. Los resultados de la experiencia indicaron un alto grado de éxito, observándose un aumento del aprendizaje, y por tanto, del rendimiento académico del estudiantado. La experiencia educativa, con un 33% de carácter presencial y un 67% de carácter virtual, resultó ser una alternativa a las prácticas convencionales de alta presencialidad para su implementación en épocas de pandemia.

For the past three decades, nanoscience has widely affected many areas in physics, chemistry, and engineering, and has led to numerous fundamental discoveries as well as applications and products. Concurrently, quantum science and technology has developed into a cross-disciplinary research endeavour connecting these same areas and holds a burgeoning commercial promise. Although quantum physics dictates the behaviour of nanoscale objects, quantum coherence, which is central to quantum information, communication and sensing has not played an explicit role in much of nanoscience. This Review describes fundamental principles and practical applications of quantum coherence in nanoscale systems, a research area we call quantum-coherent nanoscience. We structure this manuscript according to specific degrees of freedom that can be quantum-coherently controlled in a given nanoscale system such as charge, spin, mechanical motion, and photons. We review the current state of the art and focus on outstanding challenges and opportunities unlocked by the merging of nanoscience and coherent quantum operations., Comment: 34 pages, 6 figures, 2 boxes

The spectral overlap between stimulated emission (SE) and absorption from dark states (i.e. charges and triplets) especially in the near-infrared (NIR), represents one of the most effective gain loss channel in organic semiconductors. Recently, bottom-up synthesis of atomically precise graphene nanostructures, or nanographenes (NGs), has opened a new route for the development of environmentally and chemically stable materials with optical gain properties. However, also in this case, the interplay between gain and absorption losses has hindered the attainment of efficient lasing action in the NIR. Here, we demonstrate that the introduction of two fluoranthene imide groups to the NG core leads to a more red-shifted emission than the precursor NG molecule (685 vs. 615 nm) and also with a larger Stokes (45 nm vs. 2 nm, 1026 cm-1 vs. 53 cm-1, respectively). Photophysical results indicate that, besides the minimisation of ground state absorption losses, such substitution permits to suppress the detrimental excited state absorption in the NIR, which likely arises from a dark state with charge-transfer character. This has enabled NIR lasing (720 nm) from all-solution processed distributed feedback devices with one order of magnitude lower thresholds than those of previously reported NIR-emitting NGs. This study represents an advance in the field of NGs and, in general, organic semiconductors photonics, towards the development of cheap and stable NIR lasers. G.M.P. thanks Fondazione Cariplo for financial support (grant n° 2018-0979). R.M.M., P.G.B., J.M.V., J.A.Q. and M.A.D.G. acknowledge funding from the Spanish Ministry of Economy and Competitiveness (MINECO), the European Regional Development Fund (FEDER) and European Social Funds (ESF; grant n° MAT2015-66586-R and FPI fellowship BES-2016-077681). Q.C., K.M. and A.N. are grateful for the financial support by the Max Planck Society and the ANR-DFG NLE Grant GRANAO by DFG 431450789. K.M. acknowledges a fellowship from Gutenberg Research College, Johannes Gutenberg University Mainz. R.K. and A.N. appreciate the support by the Okinawa Institute of Science and Technology Graduate University. Y.I. and A.N acknowledge financial support from the Japan Society of Promotion Science Program for Advancing Strategic International Networks to Accelerate the Circulation of Talented Researchers.

The determination of the ground state of quantum many-body systems via digital quantum computers rests upon the initialization of a sufficiently educated guess. This requirement becomes more stringent the greater the system. Preparing physically-motivated ans\"{a}tze on quantum hardware is therefore important to achieve quantum advantage in the simulation of correlated electrons. In this spirit, we introduce the Gutzwiller Wave Function (GWF) within the context of the digital quantum simulation of the Fermi-Hubbard model. We present a quantum routine to initialize the GWF that comprises two parts. In the first, the noninteracting state associated with the $U = 0$ limit of the model is prepared. In the second, the non-unitary Gutzwiller projection that selectively removes states with doubly-occupied sites from the wave function is performed by adding to every lattice site an ancilla qubit, the measurement of which in the $|0\rangle$ state confirms the projection was made. Due to its non-deterministic nature, we estimate the success rate of the algorithm in generating the GWF as a function of the lattice size and the interaction strength $U/t$. The scaling of the quantum circuit metrics and its integration in general quantum simulation algorithms are also discussed., Comment: 5 pages + Supplemental Material

When magnetic atoms are inserted inside a superconductor, the superconducting order is locally depleted as a result of the antagonistic nature of magnetism and superconductivity. Thereby, distinctive spectral features, known as Yu–Shiba–Rusinov states, appear inside the superconducting gap. The search for Yu–Shiba–Rusinov states in different materials is intense, as they can be used as building blocks to promote Majorana modes suitable for topological quantum computing. Here, the first observation of Yu–Shiba–Rusinov states in graphene, a non-superconducting 2D material, and without the participation of magnetic atoms, is reported. Superconductivity in graphene is induced by proximity effect brought by adsorbing nanometer-scale superconducting Pb islands. Using scanning tunneling microscopy and spectroscopy the superconducting proximity gap is measured in graphene, and Yu–Shiba–Rusinov states are visualized in graphene grain boundaries. The results reveal the very special nature of those Yu–Shiba–Rusinov states, which extends more than 20 nm away from the grain boundaries. These observations provide the long-sought experimental confirmation that graphene grain boundaries host local magnetic moments and constitute the first observation of Yu–Shiba–Rusinov states in a chemically pure system. This work was supported by AEI and FEDER under projects MAT2016-80907-P and MAT2016-77852-C2-2-R (AEI/FEDER, UE), by the Fundación Ramón Areces, and by the Comunidad de Madrid NMAT2D-CM program under grant S2018/NMT-4511. J.F.R. acknowledges financial support European Regional Development Fund Project No. NORTE-01-50145- FEDER-000019, and the UTAPEXPL/NTec/0046/2017 projects, as well as Generalitat Valenciana funding Prometeo2017/139 and MINECO Spain (Grant No. MAT2016-78625-C2). J.L.L is grateful for financial support from the Academy of Finland Projects Nos. 331342 and 336243.

We study the electronic properties of the heterobilayer of vanadium and iron oxychlorides, VOCl and FeOCl, two layered air stable van der Waals insulating oxides with different types of antiferromagnetic order in bulk: VOCl monolayers are ferromagnetic (FM) whereas the FeOCl monolayers are antiferromagnetic (AF). We use density functional theory (DFT) calculations, with Hubbard correction that is found to be needed to describe correctly the insulating nature of these compounds. We compute the magnetic anisotropy and propose a spin model Hamiltonian. Our calculations show that interlayer coupling in weak and ferromagnetic so that magnetic order of the monolayers is preserved in the heterobilayers providing thereby a van der Waals heterostructure that combines two monolayers with different magnetic order. Interlayer exchange should lead both to exchange bias and to the emergence of hybrid collective modes that that combine FM and AF magnons. The energy band of the heterobilayer show a type II band alignment, and feature spin-splitting of the states of the AF layer due to the breaking of the inversion symmetry., Comment: 6 pages, 3 figures

Nowadays, there exist many physical realizations of qubits for quantum computing. Some modern and prominent examples of types of quantum computer platforms are the superconducting qubits, spin qubits, trapped-ion qubits, photonic qubits and topological qubits. In this document, we overview the underlying physical principles of three of these platforms: superconducting qubits, spin qubits in semiconductors and trapped-ion qubits. This work is also meant to serve as an introduction to these technologies. This document is organized as follows. First, we introduce the so called DiVincenzo criteria [3] that de ne the requirements that a system has to meet to be useful as a quantum computer, with a brief explanation of the decoherence and the Bloch sphere. Second, we go through the three quantum computer platforms. The second part begins with an introduction to the superconducting qubits by explaining some basic concepts of superconductivity such as the Meissner effect and the flux quantization on a superconducting ring. This is done in order to understand the basics of the Josephson junctions used in this type of qubits. Then, the three main types of superconducting qubits are explained. Superconducting qubits can be divided on three main types depending on the variable chosen to encode the qubit state: charge qubits, phase qubits and flux qubits. In the sections dedicated to the charge qubits, the Cooper pair box, which is the predecessor to the transmon qubit, is explained in order to understand the transmon qubits. We focus our attention mainly on the transmon qubit because it seems to be the most popular type of superconducting qubit. In the following sections, the spin qubits and the trapped-ion qubits are also explained. There are also different possibilities for implementing spin qubits like, for example, in NV-centers in a diamond lattice, color centers, spins on molecules, shallow dopants or electrostatically confined quantum dots in semiconductors. We focus on the latter. For trapped-ion qubits there are different state encoding possibilities depending on the energy levels used as computational subspace so, for example, we have Zeeman, hyperfine, optical and fine-structure trapped-ion qubits. Each section corresponding to the different qubit implementations explained on this work follows the same basic scheme. The explanation of each implementation is done by showing how it satisfies the five DiVincenzo criteria.

We revisit quantum phase estimation algorithms for the purpose of obtaining the energy levels of many-body Hamiltonians and pay particular attention to the statistical analysis of their outputs. We introduce the mean phase direction of the parent distribution associated with eigenstate inputs as a new post-processing tool. By connecting it with the unknown phase, we find that if used as its direct estimator, it exceeds the accuracy of the standard majority rule using one less bit of resolution, making evident that it can also be inverted to provide unbiased estimation. Moreover, we show how to directly use this quantity to accurately find the energy levels when the initialized state is an eigenstate of the simulated propagator during the whole time evolution, which allows for shallower algorithms. We then use IBM Q hardware to carry out the digital quantum simulation of three toy models: a two-level system, a two-spin Ising model and a two-site Hubbard model at half-filling. Methodologies are provided to implement Trotterization and reduce the variability of results in noisy intermediate scale quantum computers., Comment: 16 pages, 15 figures

Quantum confinement of graphene Dirac-like electrons in artificially crafted nanometer structures is a long sought goal that would provide a strategy to selectively tune the electronic properties of graphene, including bandgap opening or quantization of energy levels However, creating confining structures with nanometer precision in shape, size and location, remains as an experimental challenge, both for top-down and bottom-up approaches. Moreover, Klein tunneling, offering an escape route to graphene electrons, limits the efficiency of electrostatic confinement. Here, a scanning tunneling microscope (STM) is used to create graphene nanopatterns, with sub-nanometer precision, by the collective manipulation of a large number of H atoms. Individual graphene nanostructures are built at selected locations, with predetermined orientations and shapes, and with dimensions going all the way from 2 nanometers up to 1 micron. The method permits to erase and rebuild the patterns at will, and it can be implemented on different graphene substrates. STM experiments demonstrate that such graphene nanostructures confine very efficiently graphene Dirac quasiparticles, both in zero and one dimensional structures. In graphene quantum dots, perfectly defined energy band gaps up to 0.8 eV are found, that scale as the inverse of the dots linear dimension, as expected for massless Dirac fermions, Main Manuscript and Supporting Information

Nonreciprocal spin waves have a chiral asymmetry so that their energy is different for two opposite wave vectors. They are found in atomically thin ferromagnetic overlayers with in-plane magnetization and are linked to the antisymmetric Dzyaloshinskii-Moriya surface exchange. We use an itinerant fermion theory based on first-principles calculations to predict that nonreciprocal magnons can occur in Fe3GeTe2, the first stand-alone metallic two-dimensional crystal with out-of-plane magnetization. We find that both the energy and lifetime of magnons are nonreciprocal, and we predict that acoustic magnons can have lifetimes up to hundreds of picoseconds, orders of magnitude larger than in other conducting magnets., N.M.R.P. acknowledges support from the European Commission through the project Graphene-Driven Revolutions in ICT and Beyond (Ref. No. 881603 -Core 3), and the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2013, COMPETE2020, PORTUGAL2020, FEDER, and the Portuguese Foundation for Science and Technology (FCT) through Projects No. PTDC/FISNAN/3668/2013 and No. POCI-01-0145-FEDER-028114. J.F.-R. acknowledges financial support from FCT for Project No. UTAP-EXPL/NTec/0046/2017, as well as Generalitat Valenciana funding Prometeo2017/139 and MINECO-Spain (Grant No. MAT2016-78625-C2). A.T.C. acknowledges the use of computer resources at MareNostrum and technical support provided by the Barcelona Supercomputing Center (RES-FI-2019-2-0034, RES-FI-2019-3-0019).

The efficient synthesis and electronic properties of two large‐size cove‐edged nanographenes (NGs), CN1 and CN2, are presented. X‐ray crystallographic analysis reveals a contorted backbone for both molecules owing to the steric repulsion at the inner cove position. Noticeably, the dominant structures of these molecules contain four (for CN1) or six (for CN2) localized C=C double bonds embedded in nine (for CN1) or twelve (for CN2) aromatic sextet rings according to Clar's formula, which is supported by bond length analysis and theoretical (NICS, ACID) calculations. Furthermore, Raman spectra exhibit a band associated with the longitudinal CC stretching mode of olefinic double bonds. Owing to the existence of the additional olefinic bonds, both compounds show a small band gap (1.84 eV for CN1 and 1.37 eV for CN2). They also display moderate fluorescence quantum yield (35 % for CN1 and 50 % for CN2) owing to the contorted geometry, which can suppress aggregation in solution. J.W. acknowleges financial support from the MOE Tier 3 programme (MOE2014-T3-1-004) and NRF Investigatorship (NRF-NRFI05-2019-0005). J.C. acknowledges MINECO and Junta de Andalucía of Spain projects (PGC2018-098533-BI00 and UMA18FEDERJA057). M.A.D.-G. and R.M.-M. thank support from MINECO through the research project MAT2015-66586-R and the FPI fellowship (no. BES-2016-077681), respectively.

Atomic-sized contacts of iron, created in scanning tunneling microscope break junctions, present unusually high values of conductance compared to other metals. This result is counterintuitive since, at the nanoscale, body-centered-cubic metals are expected to exhibit lower coordination than face-centered-cubic metals. In this work we first perform classical molecular dynamics simulations of the contact rupture, using two different interatomic potentials. The first potential is isotropic, and produces mostly single-atom prerupture contacts. The second potential accounts for the directional bonding in the materials, and produces mostly highly coordinated prerupture structures, generally consisting of more than one atom in contact. To compare the two different types of structures with experiments, we use them as input to density functional theory electronic transport calculations of the conductance. We find that the highly coordinated structures, obtained from the anisotropic potential, yield higher conductances which are statistically in better agreement with those measured for body-centered-cubic iron. We thus conclude that the directional bonding plays an important role in body-centered-cubic metals. This work was supported by the Generalitat Valenciana through PROMETEO2017/139 and GENT (CDEIGENT2018/028), the Spanish government through Grants No. MAT2016-78625-C2-1-P and No. FIS2016-80434-P, and the Spanish Ministry of Science and Innovation, through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000805-M), by Comunidad Autónoma de Madrid through Grant No. S2018/NMT-4321 (NanomagCOST-CM), by the Fundación Ramón Areces, and by the European Union Graphene Flagship under Grant No. 604391.

Nanographenes with zigzag edges are predicted to manifest non-trivial pi-magnetism resulting from the interplay of hybridization of localized frontier states and Coulomb repulsion between valence electrons. This provides a chemically tunable platform to explore quantum magnetism at the nanoscale and opens avenues toward organic spintronics. The magnetic stability in nanographenes is thus far limited by the weak magnetic exchange coupling which remains below the room temperature thermal energy. Here, we report the synthesis of large rhombus-shaped nanographenes with zigzag periphery on gold and copper surfaces. Single-molecule scanning probe measurements unveil an emergent magnetic spin-singlet ground state with increasing nanographene size. The magnetic exchange coupling in the largest nanographene, determined by inelastic electron tunneling spectroscopy, exceeds 100 meV or 1160 K, which outclasses most inorganic nanomaterials and remarkably survives on a metal electrode., 4 figures plus supplementary information

Triangular zigzag nanographenes, such as triangulene and its π‐extended homologues, have received widespread attention as organic nanomagnets for molecular spintronics, and may serve as building blocks for high‐spin networks with long‐range magnetic order, which are of immense fundamental and technological relevance. As a first step towards these lines, we present the on‐surface synthesis and a proof‐of‐principle experimental study of magnetism in covalently bonded triangulene dimers. On‐surface reactions of rationally designed precursor molecules on Au(111) lead to the selective formation of triangulene dimers in which the triangulene units are either directly connected through their minority sublattice atoms, or are separated via a 1,4‐phenylene spacer. The chemical structures of the dimers have been characterized by bond‐resolved scanning tunneling microscopy. Scanning tunneling spectroscopy and inelastic electron tunneling spectroscopy measurements reveal collective singlet–triplet spin excitations in the dimers, demonstrating efficient intertriangulene magnetic coupling., The on‐surface synthesis of covalently bonded triangulene dimers with or without a 1,4‐phenylene spacer was achieved on Au(111). Scanning tunneling spectroscopy measurements revealed collective magnetism in the dimers in the form of singlet–triplet spin excitations, demonstrating efficient and tunable intertriangulene magnetic coupling.

We address the coexistence of massless and massive topological edge states at the interface between two materials with different topological phases. We modify the well-known Bernevig-Hughes-Zhang model to introduce a smooth function describing the band inversion and the band bending due to electrostatic effects between the bulk of the quantum well and the vacuum. Within this minimal model we identify distinct parameter sets that can lead to the coexistence of the two types of edge states and that determine their number and characteristics. We propose several experimental setups that could demonstrate their presence in two-dimensional topological systems, as well as ways to regulate or tune the contribution of the massive edge states to the conductance of associated electronic devices. Our results suggest that such states may also be present in novel two-dimensional van der Waals topological materials., The work of T.L.v.d.B. and D.B. was supported by the Spanish Ministerio de Economía y Competitividad (MINECO) through Project No. FIS2014-55987-P, by Spanish Ministerio de Ciecia, Innovation y Universidades (MICINN) through Project No. FIS2017-82804-P, and by the Transnational Common Laboratory Quantum-ChemPhys. M.R.C. acknowledges funding from the Spanish Government through Project No. MAT2017-88377-C2-2-R (AEI/FEDER UE) and the Generalitat Valenciana through Grant No. Cidegent2018004.

Gate-based quantum computers can in principle simulate the adiabatic dynamics of a large class of Hamiltonians. Here we consider the cyclic adiabatic evolution of a parameter in the Hamiltonian. We propose a quantum algorithm to estimate the Berry phase and use it to classify the topological order of both single-particle and interacting models, highlighting the differences between the two. This algorithm is immediately extensible to any interacting topological system. Our results evidence the potential of near-term quantum hardware for the topological classification of quantum matter., Comment: Main text: 4 pages, 3 figures; Supplemental material: 9 pages, 9 figures

The emergence of local moments in graphene zigzag edges, grain boundaries, vacancies and sp3 defects has been widely studied theoretically. However, conclusive experimental evidence is scarce. Recent progress in on-surface synthesis has made it possible to create nanographenes, such as triangulenes, with local moments in their ground states, and to probe them using scanning tunneling microscope (STM) spectroscopy. Here we review the application of the theory of sequential and cotunneling transport to relate the dI/dV spectra with the spin properties of nanographenes probed by STM. This approach permits us to connect the dI/dV with the many-body energies and wavefunctions of the graphene nanostructures. We apply this method describing the electronic states of the nanographenes by means of exact diagonalization of the Hubbard model within a restricted Active Space. This permits us to provide a proper quantum description of the emergence of local moments in graphene and its interplay with transport. We discuss the results of this theory in the case of diradical nanographenes, such as triangulene, rectangular ribbons and the Clar’s goblet, that have been recently studied experimentally by means of STM spectroscopy. This approach permits us to calculate both the dI/dV spectra, that yields excitation energies, as well as the atomically resolved conductivity maps, that provide information on the wavefunctions of the collective spin modes. We acknowledge financial support from Ministry of Science and Innovation of Spain (grant numbers PID2019-106114GB-I00 and PID2019- 109539GB), from MINECO-Spain (Grant No. MAT2016-78625-C2) and from the Portuguese Fundação para a Ciência e a Tecnologia (FCT) for the projects P2020-PTDC/FIS-NAN/4662/2014, P2020-PTDC/FIS-NAN/3668/2014 and UTAPEXPL/NTec/0046/2017 projects. JFR acknowledges Generalitat Valenciana funding (Prometeo2017/139). R. O. acknowledge ACIF/2018/175 (Generalitat Valenciana and Fondo Social Europeo).

In topological systems, a modulation in the gap onset near interfaces can lead to the appearance of massive edge states, as were first described by Volkov and Pankratov. In this work, we study graphene nanoribbons in the presence of intrinsic spin-orbit coupling smoothly modulated near the system edges. We show that this space modulation leads to the appearance of Volkov-Pankratov states, in addition to the topologically protected ones. We obtain this result by means of two complementary methods, one based on the effective low-energy Dirac equation description and the other on a fully numerical tight-binding approach, finding excellent agreement between the two. We then show how transport measurements might reveal the presence of Volkov-Pankratov states, and discuss possible graphene-like structures in which such states might be observed., Comment: 12 pages, 8 figures

The discovery of ferromagnetic order in monolayer 2D crystals has opened a new venue in the field of two dimensional (2D) materials. 2D magnets are not only interesting on their own, but their integration in van der Waals heterostructures allows for the observation of new and exotic effects in the ultrathin limit. The family of Chromium trihalides, CrI$_3$, CrBr$_3$ and CrCl$_3$, is, so far, the most studied among magnetic 2D crystals. In this mini-review, we provide a perspective of the state of the art of the theoretical understanding of magnetic 2D trihalides, most of which will also be relevant for other 2D magnets, such as vanadium trihalides. We discuss both the well-established facts, such as the origin of the magnetic moment and magnetic anisotropy and address as well open issues such as the nature of the anisotropic spin couplings and the magnitude of the magnon gap. Recent theoretical predictions on Moir\' e magnets and magnetic skyrmions are also discussed. Finally, we give some prospects about the future interest of these materials and possible device applications., Comment: This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Nano Letters, copyright \c{opyright} American Chemical Society after peer review

La computación clásica forma parte de nuestro día a día y ha sido uno de los pilares que ha impulsado la innovación en las últimas décadas. Sin embargo, hay problemas que esta tecnología no es capaz de resolver o es muy poco eficiente hacerlo de esta manera. Aquí es donde entra en juego la computación cuántica, campo en el cual se están alcanzando progresos significativos. La principal diferencia entre la computación clásica y la cuántica es que en esta última se hace uso de fenómenos cuánticos, tales como la superposición y el entrelazamiento. Para ello la computación cuántica se basa en el uso de qubits o bits cuánticos, dejando de lado los bits clásicos y los sistemas lógicos empleados por los sistemas informáticos convencionales. Esta tecnología resulta de gran interés actualmente por su enorme potencial, que supone la posibilidad de revolucionar el mundo de la computación. Una misma tarea puede tener diferente complejidad en computación clásica y en computación cuántica, lo que ha dado lugar a una gran expectación. También permite la resolución de problemas intratables anteriormente. En general, los ordenadores cuánticos, debido a su gran capacidad de manejo de datos, nos ofrecen la posibilidad de impulsar grandes avances en diversos campos, desde la ingeniería hasta la investigación farmacéutica, por ejemplo. En este trabajo se aborda el estudio del algoritmo cuántico de Grover, que resuelve el problema de encontrar una entrada en una base de datos desestructurada. En primer lugar se introducen los conceptos básicos para la comprensión del algoritmo, tales como el oráculo y la amplificación de amplitud. Posteriormente se tratan las mejoras respecto de los algoritmos de búsqueda clásicos y el hecho de que el algoritmo de Grover es óptimo. Esto completa la parte de desarrollo teórico. Posteriormente se presenta una componente de simulación en la plataforma IBM Quantum Experience para las diferentes situaciones propuestas. Más tarde se lleva a cabo la implementación real del algoritmo en los ordenadores cuánticos de IBM así como la implementación mitigando en cierta medida el error propio de los ordenadores cuánticos. Finalmente, se comentan algunas aplicaciones dentro del gran abanico de aplicaciones existentes a día de hoy.

This project will tackle the theoretical and computational study of quantum transport in graphene atomic-sized contacts. In this study, we will consider different scenarios, sizes, and shapes of the graphene electrodes and how they are connected.

Chemically synthesized zigzag-edged nanographenes (NG) have recently demonstrated great success as the active laser units in solution-processed organic distributed feedback (DFB) lasers. Here, we report the first observation of dual amplified spontaneous emission (ASE) from a large-size NG derivative (with 12 benzenoid rings) dispersed in a polystyrene film. ASE is observed simultaneously at the 685 and 739 nm wavelengths, which correspond to different transitions of the photoluminescence spectrum. Ultrafast pump-probe spectroscopy has been used to ascertain the underlying photophysical processes taking place in the films. DFB lasers, based on these materials and top-layer nanostructured polymeric resonators (i.e., one or two-dimensional surface relief gratings), have been fabricated and characterized. Lasers emitting close to either one of the two possible ASE wavelengths, or simultaneously at both of them, have been prepared by proper selection of the resonator parameters. The Alicante team was funded by Spanish Government (MINECO) and European Community (FEDER), grant number MAT2015-66586-R. The researcher R.M-M was funded by a MINECO FPI fellowship (No. BES-2016-077681). The Singapore team was funded by the NRF Investigatorship programme (NRF-NRFI05-2019-0005). The Milan team has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 816313). G.M.P. acknowledges funding from Fondazione Cariplo, grant No. 2018-0979. C.D. and S.S. acknowledge funding from ERC Starting Grant SOLENALGAE (No. 679814).

10 pags., 7 figs., The increasing number of solution-processed laser compounds that can be implemented as low-cost, flexible, and/or integrated devices, makes necessary the development of reliable methods to delineate all their amplifying signatures and thus to open the door to appropriate cross-sample comparisons. Seeking to solve this problem, a new formalism to retrieve the losses and the optical gains from Amplified Spontaneous Emission (ASE) spectra as a function of the excitation density has been recently reported. In this manuscript, we explore the potential of this methodology to unveil relevant information on the photonic properties of the waveguiding devices and on the photophysics of the active materials. We demonstrate that the Variable Pump Intensity method opens the door to understand the relationship between the ASE thresholds and the optical gains and losses, it enables the extraction of the scattering/modal losses of the passive devices, and it can unveil the presence of leaky-modes and excited state absorption. In contrast, it does not perform too well in samples with multiple active species in its current implementation. We have substantiated all these findings using organic semiconductor thin films, several dye-doped polymer thin films and solutions of boron hydride., The researchers from the University of Alicante and LC acknowledge financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) and the European FEDER funds through Grant numbers MAT2015-66586-R and MAT2017-83856-C3-1, respectively.

Carbon-bridged oligo(p-phenylenevinylene)s (COPVn with repeating unit n = 1–6) have demonstrated great success as laser dyes for thin-film organic lasers. The excellent photostability observed in the longer homologues is, however, not present in the blue-emitting shorter compounds COPV1 and COPV2, attributed to the unprotected terminal positions that can degrade by photoreaction in the excited state. Here we report the synthesis of various COPV1 and COPV2 derivatives functionalized at the terminal positions with two types of sterically bulky protecting substituents: Tip (2,4,6-triisopropylphenyl) and tert-butyl (t-Bu) groups. Such molecular designs aim at preventing such photodegradation processes and thus to improve their stability. The efficacy of kinetic isotope effect for stabilization is also examined for COPV2, by the addition at terminal positions of deuterium atoms. Absorption, photoluminescence (PL), including PL quantum yield, and amplified spontaneous emission (ASE) studies have been conducted in polystyrene films doped with each of the derivatives. Significant and slight improvements of the ASE photostability are observed for the compounds with Tip groups and deuterium, respectively. Installation of substituents slightly affects the ASE wavelength within the blue spectral region, that is 385–413 nm and 462–474 nm, for COPV1 and COPV2, respectively. Financial support from Spanish Ministerio de Economía y Competitividad (MINECO) and the European FEDER funds through Grant MAT2015-66586-R is gratefully acknowledged. This work was partially supported by MEXT and JSPS KAKENHI Grant Numbers JP16H04106 and JP19H05716 to HT and JP19H0549 to EN.

El proyecto de esta red titulado “Adaptación de asignaturas del máster en Ciencia de Materiales a la modalidad semipresencial” ha pretendido iniciar la reflexión sobre la posibilidad de reducir la presencialidad en la docencia del máster en Ciencia de Materiales, con la finalidad de facilitar que los alumnos puedan compaginar mejor los estudios de este máster con otras actividades. En un primer paso, se ha planteado planificar la docencia de tres asignaturas del máster (una del módulo fundamental y dos optativas) en forma semipresencial. De este modo, si esta nueva metodología es bien aceptada, podría plantearse su extensión al resto de asignaturas. Las asignaturas seleccionadas para este estudio son: “Técnicas de caracterización I: Dispersión de rayos X, neutrones y electrones. Microscopias”; “Materiales compuestos”; e “Introducción a la ciencia y tecnología de los materiales de carbón”. La adaptación de los métodos didácticos de estas asignaturas a la docencia semipresencial implica la preparación y selección de una serie de materiales adicionales a los que se han usado habitualmente. Con el fin de valorar el interés de los alumnos por esta posible modificación de la metodología de docencia en el Máster en Ciencia de Materiales, en el curso actual se realizó una encuesta a los alumnos del mismo. Los resultados de ésta indican que la incorporación de la docencia semipresencial sería una iniciativa bien recibida por el alumnado.

Two-dimensional (2D) massive Dirac electrons possess a finite Berry curvature, with Chern number $\pm 1/2$, that entails both a quantized dc Hall response and a subgap full-quarter Kerr rotation. The observation of these effects in 2D massive Dirac materials such as gapped graphene, hexagonal boron nitride or transition metal dichalcogenides (TMDs) is obscured by the fact that Dirac cones come in pairs with opposite sign Berry curvatures, leading to a vanishing Chern number. Here, we show that the presence of spin-orbit interactions, combined with an exchange spin splitting induced either by diluted magnetic impurities or by proximity to a ferromagnetic insulator, gives origin to a net magneto-optical Kerr effect in such systems. We focus on the case of TMD monolayers and study the dependence of Kerr rotation on frequency and exchange spin splitting. The role of the substrate is included in the theory and found to critically affect the results. Our calculations indicate that state-of-the-art magneto-optical Kerr spectroscopy can detect a single magnetic impurity in diluted magnetic TMDs., 8 pages, 3 figures

Quantum computing is the field that studies computation using quantum mechanical systems, exploiting properties such as superposition or entanglement. The focus of this project will be on quantum phase estimation algorithms. The formalism commonly used to represent quantum algorithms as quantum circuits composed by qubits and quantum gates will be presented. Then, we will be able to explain the quantum Fourier transform (that is exponentially faster than its classical analogue) and three quantum phase estimation algorithms: Kitaev’s phase estimation (KPEA), the phase estimation algorithm based on QFT (PEA) and the iterative quantum phase estimation algorithm based on a semiclassical Fourier transform (IPEA). We will use the Qiskit framework in order to run simulations of such algorithms, and even run them in real IBM Q Experience quantum computers (specifically, we will use the 5 qubit computer ibmq_essex). Statistical post-processing techniques will be essential in order to extract a phase estimation from the results obtained. We will use two post-processing techniques: the majority and the average rule. The performance of these methods applied to the results of several simulations and executions in ibmq_essex will be studied. At last, we will talk about the possible applications of phase estimation algorithms. Phase estimation is used as a subroutine in the field of quantum simulation, allowing us to obtain several magnitudes of a quantum system such as the energy levels. We will present an efficient quantum algorithm for factoring called Shor’s algorithm. The cost of factorization with a classical computer increases exponentially with the size of the input, so this is a example of a task that cannot be solved efficiently on a classical computer, but can be solved efficiently by a quantum computer. Phase estimation is also used in the field of quantum metrology. Specifically, an N-V center can be used to measure magnetic fields with high sensitivity and spatial resolution operating at room temperature thanks to a measuring protocol based on phase estimation.

As the first of a series of molecular solenoids, two classes of dithia[7]helicenes (coil-shaped molecules with sulfur atoms integrated within a helical conjugated system) have been devised and synthesized to be used in molecular electronics. We used a modular assembly of fragments using Pd catalyzed coupling reactions and a final photocyclization step for the syntheses; this strategy gave us straightforward access to helicenes bearing thiophene end rings with either exo or endo topologies. Unequivocal structural characterization was carried out by X-ray crystallography. In the solid state, their crystal architectures show little similarities; both can be considered an ensemble of heterochiral dimers (P/M) that are themselves very different in nature in light of their main pairing interactions. On a gold surface, the effect of the sulfur atom is to strengthen their binding to the electrodes, as manifested by scanning tunneling microscopy (STM) performed at room temperature. Different coating patterns were observed for each class of molecule, although the most prominent finding is that we could see resolved STM images of a single molecule, with a full display of its inherent chirality under room temperature conditions. Financial support by the Spanish Ministry of Economy and Competitiveness (MAT2016-78625-C2-1-P and MAT2016-78625-C2-2-P), the Generalitat Valenciana (PROMETEO/2017/139 and CDEIGENT/2018/028), and finally the University of Alicante (VIGROB-285 and 188) is gratefully acknowledged.

In the present work a new material based on the recently developed graphite flakes-SiC particles/metal composite, is described. The latter was processed by gas-pressure infiltration of the liquid metal into a preform obtained by packing a mixture of graphite flakes and SiC particles. Its microstructure consists of alternating layers of oriented graphite flakes and metal-particles composite, and, thus, it is highly anisotropic. Its highest thermal conductivity (>300 Wm−1K−1), attained in the plane parallel to the flakes plane, makes it suitable for heat sinking applications. Replacing SiC by particles of similar size and of ferromagnetic nature (Fe, Co and Ni), a material with moderate-to-high magnetic permeability and reasonably high thermal conductivity, has been produced. Mixtures of packed magnetic particles and graphite flakes were infiltrated with pure magnesium. In order to avoid chemical reaction, Co and Ni particles were carbon coated. Optimizing the combination of thermal conductivity and magnetic properties requires proper control of liquid metal infiltration variables, such as, temperature, pressure and contact time before metal solidification. The authors acknowledge partial financial support from the “Ministerio de Ciencia e Innovación” (grant MAT2016-77742-C2-2-P).