In the context of spintronics development using semiconductors, new phenomena have been discovered and begin to be explored at the nanoscale. Spin injection in semiconductors from a ferromagnetic metal and semiconductors doping with magnetic atoms opened the way to new devices conception using both the electron charge and spin. But these topics raised also new questions concerning the physics of impurities and interfaces that play a crucial role when devices shrink to nanoscale. The goal of the SSAS project is to address these questions of magnetism in semiconductors heterostructures using Scanning Tunneling Microscopy (STM) techniques. Innovating techniques will be developed and applied to semiconductors samples to probe magnetic properties down to the atomic scale, namely the Scanning Tunneling Spectroscopy (STS), the Spin-Polarized STM (SP-STM) and the Inelastic Electrons Tunneling Spectroscopy (IETS). A first part of the project will be devoted to nanomagnetism of heterostructures. The local magnetization behavior and the magnetic anisotropy will be probed near semiconductor interfaces (for example on Fe/GaAs hybrid structures used in spin injection experiments), and in magnetically doped semiconductors (in the ferromagnetic material Ga1-xMnxAs). SP-STM will be used in these samples for the first time. Using the ability of tunneling spectroscopy to probe the local electronic density of states, the band structure modification of semiconductors will be investigated when one introduce magnetic impurities in a semiconductors matrix. Magnetic doping will be explored with two points of view: the band structure of ferromagnetic samples strongly doped, and the local electronic modification brought by single magnetic atoms on the surrounded semiconductors material. In this context, the effect of magnetic doping will also be studied in semiconductors nanostructures presenting discrete electronic structure as quantum dots. Finally, a new type of approach is suggested. Instead of studing samples used for actual studies in spintronics or nanoeletronics, the next step of future devices will be explored using structures containing only few magnetic atoms. STM offers the possibility to manipulate individual atoms on a surface and to construct artificial structures of the whished shape and size. The STM atomic manipulation will be developed in this project on semiconductors surfaces with magnetic atoms. The magnetic properties of structure with two or three atoms will then be investigated by spin dependent spectroscopy, in particular the magnetic coupling existing between them and the spin orientation of each as compare to the others. The specificity of the magnetic interaction in case of semiconductor environment will be extract as compare to metallic samples.

In this project we will develop novel tools for investigating mesoscopic physics through thermodynamic studies. Regarding the heat conduction, we will measure thermal conductance of composite fermions, implement heat interferometers, and explore the correlations between adjacent edge channels, which can induce neutral modes. We will focus on the study of correlated electron states in low-dimensional quantum systems. The experiments will be performed in the integer and fractional quantum Hall regimes.

This project gets inspiration from living cells, where information processing and decision-making at the molecular level rely on chemical reaction networks (CRNs) that are out of thermodynamic equilibrium. In particular, chemical oscillators clock important cellular rhythms, such as the cell cycle and the circadian rhythm. Here we combine two state-of-the-art technologies to engineer time-responsive, enzyme-free DNA networks outside cells, in particular synthetic oscillators. On the one hand, the topology and the dynamics of the engineered network are encoded using strand displacement DNA hybridization reactions. On the other hand, the reaction network is maintained out of equilibrium within highly controlled open microfluidic reactors. This approach has advantages compared to the first synthetic oscillators demonstrated in 2011 that required specific enzymes to degrade nucleic acids to keep them out of equilibrium. Indeed, enzymes exhibit great variability from batch to batch and render the design of these oscillators less reliable. Alternatively, enzyme-free DNA-only reaction cascades have proved to be extremely robust, but they are not time responsive. Taking advantage of microreactors we will turn them into time-responsive systems. This could revolutionize information processing at the molecular level, as we show by implementing a concentration-controlled oscillator, inspired from the ubiquitous voltage-controlled oscillator in electronic devices.

QDOM project bridges the gap, at the nanoscale, between two yet distinct research fields: optomechanics of deformable cavities (« Cavity Optomechanics ») and cavity Quantum ElectroDynamics (« Cavity QED »). These two fields utilize an electromagnetic wave trapped in a cavity, to boost its interaction with a mechanical oscillator (in optomechanics) or with an atom (in cavity QED). QDOM project aims at exploring a hybrid interface between these two domains, using semiconductor nanostructures. Indeed, semiconductor nano-optomechanical systems have advanced rapidly over the last three years, showing record optomechanical coupling, mechanical frequencies above the GHz, and a well controlled optical and mechanical dissipation. In parallel, semiconductor Quantum Dots (QD), notably Indium Arsenide QDs in a Gallium Arsenide matrix, have made impressive progress in solid-state cavity QED: the realization of non-classical photon sources, the strong coupling regime of cavity QED, and the observation of giant non-linearity at the single photon level. QDOM project exploits all these advances of semiconductor nanostructures: indeed the chosen experimental system is a miniature GaAs disk cavity that possesses a sub-micron optical mode volume. The whispering gallery modes sustained by the structure are of very high quality factor and enable a coupling of the cavity photons both to the GHz mechanical modes of the disk and to a single InAs QD inserted into the disk. The record optomechanical coupling reached in the structure is combined with the possibility of strong coupling of the QD to the cavity mode, making miniature GaAs disks a unique platform for Quantum Dot Optomechanics. In this novel field of research proposed by the project, the aim is to control a coupled tri-partite system: a cavity photon interacts with a coherent quantum emitter (two-level atom) and with a single mechanical mode. QDOM project seeks at inspecting this novel physics paradigm, both experimentally and theoretically. The partners will first optimize the on-chip design and optomechanical properties of GaAs disk resonators embedding InAs Quantum Dots. A second part of the project aims at controlling the QD dephasing mechanisms in a cavity to amplify the QD impact in optomechanical phenomena, and then proposes to develop resonant spectroscopy experiments on a single QD coupled to a GaAs disk cavity mode. At that point first optomechanics experiments relying on the coupling to a Quantum Dot will be performed: the observation of QD-assisted optomechanical dynamical back-action, leading to the QD-assisted control of the disk mechanical motion, and then the modification by the disk mechanical motion of the resonant optical response of a QD in a cavity. These experimental developments will be carried-out in parallel with theoretical developments that aim, with a growing level of refinement, at a quantum description of the QD-optomechanics situations under study. The project involves two laboratories and brings together three teams with complementary internationally recognized expertise: an expert team in semiconductor nano-optomechanics (MPQ), an expert team in Quantum Dot cavity QED (LPN), and an expert theory team in semiconductor quantum electrodynamics and optics (MPQ). All conditions are thus met to advance in the novel nanoscience research line proposed by the project.