EPOSBP project deals with black phosphorus (BP) which has joined the 2D materials family only very recently in 2014. The first representative of this new class of materials is Graphene, isolated ten years ago, which discovery sparkled an intense research activity. However, the lack of band gap in graphene has launched a quest for new 2D materials. The field has gradually been enriched by new contenders such as hexagonal Boron Nitride (hBN) and more recently the transition metal dichalcogenides family (e.g MoS2), leading to the emergence of a broad family of 2D van der Waals materials. In the specific optoelectronic field, the progress has remained limited due to the impossibility to gather together a direct bandgap AND a high carrier mobility within the same material. In this direction, black phosphorus (BP) has attracted an explosive interest since 2014 as it displays major properties for (opto-)electronic devices: (1) high hole and electron mobilities in thin layers of exfoliated BP (~3000 cm2 V-1 s-1). (2) high (~105) ON/OFF current ratio in a transistor configuration with ambipolar characteristics. (3) the BP bandgap is predicted to remain direct from the bulk to the monolayer, making it highly interesting for optical applications. The electronic structure near the Fermi level strongly depends on the number of layers, leading to a bandgap increase from the mid infrared (0.35 eV) in the bulk to the visible range (2 eV) in monolayers. Thus BP offers a unique spectral range in the 2D landscape. However, while early 2017 results seems to highlight BPs peculiar properties in ultrathin layers, only little is known from experimental measurements. Additionally, thanks to its natural low spin-orbit coupling, the BP could be expected to very efficiently preserve the spin lifetime of the carriers, as in graphene, but offering a semiconducting gap. This would be a unique opportunity for spin transport and spintronics. The objective of EPOSBP is to investigate these unique properties of BP and, capitalizing on them, to achieve new optically active flat materials from visible to mid-infrared. The dielectric response as well as the electronic behaviors and spin injection of BP transistor will be investigated to achieve tunable and electrically driven light emission. The project is decomposed into three tasks: 1) learning basics on BP properties aiming at defining a robust spectroscopic tools package for facilitating the integration of BP in devices, 2) fabrication and characterization of devices, 3) fabrication of BP transistors and observation of electroluminescence and efficient spin transport and 4) the demonstration of spin driven light emission. EPOSBP project constitutes a broad partnership that includes the best specialists and skills on 2D Black Phosphorus and Spintronics allied with specialists of most advanced relevant spectroscopic characterization techniques, integration of 2D materials in devices and specialists capable to demonstrate the potential of BP for innovative electroluminescence and tunable spin transport devices. The strong commitment of industrial partner Thales, with key interests in the semi-conductor area, is a strong enabler toward potential TRL rise of the project.

The E-SCAPE project aims to implement position-controlled scalable single-photon emitters (SPEs) in hexagonal boron nitride (hBN). We will use an original top-down approach based on a new family of colour centres in hBN that can be locally activated using an electron beam. The SPEs present advantageous photophysical properties with, in particular, narrow and reproducible emission lines. Our roadmap includes 1. implementation of an irradiation process with in-situ monitoring yielding deterministic activation of a single emitter per irradiated site; 2. characterisation and optical control of the SPEs based on resonant laser drive, culminating in the demonstration of indistinguishable photon emission; and 3. realisation of integrated devices with electrical and optical functionalities. In a nutshell, the E-SCAPE project will provide a new avenue towards scalable integrated single-photon sources for quantum information applications.

Superconductivity is a fascinating quantum state of condensed matter. Its study and understanding have always aroused immense interest in fundamental physics, but also in materials science and its exploitation leads to numerous technological applications: lossless current transport, energy storage, quantum computation or sensors with unprecedented resolution. In 1986, the discovery of high Tc superconductivity in cuprates allowed the acceleration of enormous progress, both experimentally and theoretically, in several areas of condensed matter physics. However, the origin of high Tc superconductivity is still an unresolved problem; One of the main reasons is the complexity of the physics of cuprates resulting from multiple interactions in competitions (magnetic fluctuations, strong electronic correlations, charge-network coupling, etc.) and nearby orders (charge density wave, antiferromagnetism, pseudo-gap, etc.). The emergence of superconductivity in nickelates, structural and electronic “cousins” of cuprates, was eagerly awaited, but only postponed in 2018 in LaNiO3 / (La, Sr) MnO3 superlattices and in August 2019 in thin layers of the “Infinite phase” Nd0.8Sr0.2NiO2 / SrTiO3, due to the inherently complex chemical processes to stabilize this phase. The SUPERNICKEL project will explore the chemical, structural, physical and electronic properties of new superconducting nickelates, using a transversal approach involving the synthesis of thin films, superlattices and massive materials, the crystallochemistry of the solid, a large battery of macroscopic probes. and experimental microscopic (magneto-transport, X-ray diffraction, photoemission spectroscopy, among others) and theory. Our objectives are to determine the nature and symmetries of the superconducting state, the origin of the interaction forming Cooper pairs, by clarifying the similarities and differences between nickelates and cuprates. Over the past few months, we have focused our efforts on mastering the complex protocol allowing to stabilize the phase of infinite layers and to synthesize the superconducting nickelate.We have already obtained samples with good nominal compositions and close to superconducting instability, and we are confident that very soon, after optimizing their synthesis, we will be one of the few groups in the world to have good quality superconducting nickelates. . In parallel, we will work on other nickelate phases. The possibility of synthesizing and studying in depth, in addition to thin films and superlattices, bulk nickelates will also be a unique approach of SUPERNICKEL. We expect from the thin film / solid material comparison essential and potentially unique information on the specificity of the thin film / substrate form in the emergence of superconductivity. Our multi-approach strategy integrates design, development, detailed crystallochemical characterization, exploration of the physical and electronic properties of normal and superconducting states and theoretical modeling. The SUPERNICKEL consortium thus covers a wide range of know-how in all the essential fields and techniques necessary to tackle this problem: oxide chemistry for the synthesis of massive and thin layers, crystallography, strong correlations, magneto-transport, structure. electronics, magnetism and superconductivity. We also hope that beyond the SUPERNICKEL consortium, the dynamics of this project will become a strong pillar to consolidate and revitalize the French community working in the wider field of new superconductors.

Spin processes are highly important for the efficiency of organic solar cells and light emitting diodes, yet their role remains largely unexplored. Indeed, due to the weak spin-orbit coupling organic materials possess strict spin-selection rules and the properties of photoexcited species can therefore vary drastically, depending on the particular spin configuration. In addition, over the last years there has been tremendous progress on the development of hybrid organic-inorganic perovskite based materials, which now enable the fabrication of optoelectronic devices with remarkable performance. It has been suggested that the spin degree of freedom is relevant for photo-physical processes in these materials as well. Thus spin properties of excited states are actively investigated in very different contexts. In this project we will focus on two aspects: singlet exciton fission where a singlet exciton splits into two triplet excitons of lower energy and on spin-dependent processes in few layer hybrid- organic perovskites down to the monolayer limit where highly controlled samples can be prepared. In this project we will explore the use of broadband optically detected magnetic resonance (ODMR) spectroscopy as a powerful method to establish the microscopic nature of bi-exciton states with total spin S = 2 (quintets) formed through singlet fission. Recent experiments in LPS show that this approach allows to characterise unambiguously the molecular sites occupied by bound triplets exciton pairs. These experiments will be complemented by dielectric spectroscopy (at LPS) and pulsed magnetic resonance experiments by the Berlin partner. The combination of these techniques will characterise the microscopic positions of bound triplets in bi-exciton states, the strength of their interaction, characterised by their exchange energy, as well as their fluorescence spectrum and kinetic properties. NEEL will push the limits of the ODMR experiment to single geminate triplet-pair detection in order to observe effects obscured in ensemble measurements. The inherently high optical resolution of this technique will allow to measure the fine and ultimately the hyperfine structure parameters of the excited triplet-pair. This will provie precise information on the local molecular arrangement of the bi-exciton wavefunction. The detailed physical picture emerging from these experiments will serve as the basis for a quantitative molecular-level characterisation of the electronic structure parameters of bi-exciton states which will be developed in Bayreuth. The Bayreuth team will also perform spectroscopic experiments in order to probe the role of bi-excitons in triplet-triplet anhilation processes and optical up-conversion that are important for applications. The materials relevant for solar cell and up-conversion will probably have a complex morphology which cannot be probed in macroscopic experiments on single crystals. LPS and GEMaC will thus develop a microfluorscence based ODMR experiment. This development will also allow to probe spin-properties of Methylammonium lead halide (MAPI), a promising solar cell material, in the almost unexplored limit of chemical vapour deposition grown monolayers and few layer single crystal flakes of micrometer sizes. These samples, that have already been prepared at GEMaC/LPS, allow the creation of completely new structures based on Van-der-Waals heterojunctions and their properties are more easily tunable with gate voltages compared to bulk systems. Due to these advantages the exploration of spin dependent optical properties in MAPI-nanosheets is a very promising research direction on which the GEMaC team will concentrate. Therewithal, the MARS project will develop original spin sensitive methods to probe the properties of new photo-excited states that appear in exciton fission systems and novel materials like MAPI nanosheets with broad impact for fundamental optoelectronics and its applications.

The Mol-CoSM project, gathering three complementary french groups (Brest (1), Versailles (2) and Nancy (3)), deals with the design of new multifunctional complexes combining, in a synergetic way, molecular switching and fluorescence. Thus, in addition to the extensive synthetic work to the design new series of multifunctional systems, this project has three orientations: (i) the control of the fluorescence yield according to the nature of the fluorophore; (ii) the control of the switching parameters, such as the transition temperature and the cooperativity; (iii) the understanding of the electro-vibrational interactions between the fluorescent motif and the SCO center, so as to enhance the bi-functionality, to produce thermal bistability, both on the magnetic and fluorescent properties. The final objective is to propose new systems with enhanced multi-functionalities for potential applications such as new generations of magneto-optical switches and molecular multi-sensors.