We will discuss the application of multi-scale graph theory based methods to the detection of general structures in networks, lattices, and amorphous physical systems. These methods enable the detection of the "natural" system structures on all scales. We specifically analyze lattices and spin systems with defects and various glass formers (including an analysis based on experimental data) to ascertain dominant structures at different temperatures. We will discuss general features of the phase diagram related to this analysis. Time permitting we will also discuss the structure ascertained by response to shear.

Synthetic DNA nanostructures can be designed to replicate the structure and function of biological molecules, as well as to create novel synthetic materials [1,2]. Particularly powerful and largely unexplored is the combination of selective Watson-Crick interactionsand robust hydrophobic forces,which can be realised in amphiphilic nanostructures where non-polar tags are arranged onto engineered DNA scaffolds.
I will discuss the use of amphiphilic DNA ligands/receptors to drive attractive interactions between lipid vesicles, sharing key features with adhering biological cells and displaying an intriguing response to external stimuli [3-8].In the second part I will introduce a range of amphiphilic DNA nanostructures that reliably self-assemble into 3D macromolecular crystals, [9], finally achieving a long-standing goal of structural DNA nanotechnology.


[1] L. Di Michele, E. Eiser, Phys. Chem. Chem. Phys. 15, 3115-3129 (2013)
[2] M. R. Jones, N. C. Seeman, C. A. Mirkin, Science 347, 1260901 (2015).
[3] L. Parolini, B.M. Mognetti, J. Kotar, E. Eiser, P. Cicuta*, L. Di Michele*, Nature Commun. 6, 5948 (2015).
[4] S.F. Shimobayashi, B.M. Mognetti, L. Parolini, D. Orsi, P. Cicuta, L. Di Michele, Phys. Chem. Chem. Phys. 17, 15615-15628 (2015).

[5] L. Parolini, J. Kotar, L. Di Michele*, BM Mognetti*, ACS nano10 (2), 2392-2398
[6] L. Di Michele, S.J. Bachmann, L. Parolini, B.M. Mognetti, J. Chem. Phys. 144 (16), 161104
[7] S.J. Bachmann, J.Kotar, L.Parolini, A.Šarić, P. Cicuta, L. Di Michele*, B.M. Mognetti*, Soft Matter 12 (37), 7804-7817
[8] O.A. Amjad, B.M. Mognetti, P. Cicuta*, and L. Di Michele*, under review
[9] R.A. Brady, N.J. Brooks, P.Cicuta*, L. Di Michele*, under review

Segregation of Anhydrite in Sintered Naturally Occurring Rock Salt

Sodium chloride has been extensively studied for its behaviour when being sintered. A new approach is the utilization of rock salt. In the sinter process, the salt is getting heated just below its melting point, where the atoms are already starting to reassemble with evaporation and deposition mechanism. Rock salt consists of impurities like calcium sulfate, which gives very interesting results from pure sodium chloride. The sinter experiments are performed in partnership with the Federal Institute of Material Research and Testing (BAM) in Berlin.

Monolayer transition metal dichalcogenides (TMDs) have recently emerged as a new material system in which coupled spin-valley physics can be explored. In this talk I will discuss the optical and magneto optical properties of excitons in mono and tri – layer transitions metal dichalcogenides (TMDs).
First, I will show that optical spectroscopy in high magnetic fields B < 70 T reveals the very different nature of carriers in monolayer and bulk transition metal dichalcogenides. In mechanically exfoliated monolayer WSe2, the exciton emission shifts linearly with the magnetic field and exhibits a splitting which originates from the magnetic field induced valley splitting. The monolayer data can be described using a single particle picture with a Dirac-like Hamiltonian for massive Dirac fermions, with an additional term to phenomenologically include the valley splitting. In contrast, in bulk WSe2 where the inversion symmetry is restored, transmission measurements show a distinctly excitonic behavior with absorption to the 1s and 2s states. Magnetic field induces a spin splitting together with a small diamagnetic shift and cyclotron like behavior at high fields, which is best described within the hydrogen model. Additionally, in the monolayer material valley polarization is induced by magnetic field for a charged exciton demonstrating it’s inter valley character [1]. Furthermore I will compare the optical and mechanical properties of the exfoliated and large area single layer grown by Chemical vapor deposition. The results of the magneto optical studies suggests, surprisingly, that the 0.2% tensile strain, which is naturally present in large area CVD grown Mo based TMDs on sapphire, does not represent any serious impediment for device applications [2]. Finally, I will show our very recent results of the optical properties of the trilayer structures such as MoS2/MoSe2/MoS2 obtained by a combination of CVD growth and mechanical transfer. First, our results demonstrate a new, simple, way to encapsulate monolayer TMDS toward better optical/electrical properties. The optical properties of MoSe2 improve dramatically after embedding it into MoS2. Furthermore, while optically pumping in MoS2, the charge transfer between the layers is observed in tri layer structures leading to valley polarization of MoSe2. These results demonstrate that the spin is preserved during the charge transfer [3]. In the end, the measurements of the valley polarization of MoSe2 obtained for resonant excitation as close as 10 meV suggest that inter valley scattering is dominated by exchange interaction rather than by phonons. The experimental results are further supported by a simple model [4].


[1] A. Mitioglu, PP et al, Nano Letters 15, 4387 (2015)
[2] A. Mitioglu, PP et al, PRB 93, 165412 (2016)
[3] A. Surrente, PP et al under preparation
[4] M. Baranowski, PP et al submitted

Recent advances in optomechanics have led to outstanding discoveries. For instance, a macroscopic object (a mechanical resonator) has been cooled and measured in its quantum ground state of motion [1-2]. This technological and scientific challenge uses mechanical elements to measure weak forces and explore the interface between classical and quantum worlds. In parallel, atomically thin [3] (ex: graphene, transition metal dichalcogenides (TMD) MoS2, WSe2) have been integrated in various electronic, optical and mechanical devices. These objects are fascinating for both fundamental (electronic properties, cristal-molecule interface…) and applied aspects (soft electrodes, photo-detectors…). By combining these two domains, we envision optomechanics experiments in which the low dimensionality of the mechanical element will be an advantage (high frequency, ultra-low mass, enhanced optomechanical coupling) and an originality (electronic confinement, tunable light-matter interaction).
In this talk I will first show how to detect motion and mechanical stress within a graphitic resonator using Raman spectroscopy [4]. Such detection scheme, based on the increase of mechanical stress at resonance, link the mechanical motion of the resonator, to a shift in energy of Raman scattered photons, and represents an original scheme for optomechanical coupling.
Then, I will introduce a new type of hybrid system, consisting of an on-chip graphene NEMS suspended a few tens of nanometers above nitrogen-vacancy centres (NVCs), which are stable single-photon emitters embedded in nanodiamonds [5]. The optomechanical coupling between the graphene displacement and the NVC emission is based on near-field dipole–dipole interaction, making it suitable for nanoscale devices. These achievements hold promise for selective control of emitter arrays on-chip, optical spectroscopy of individual nano-objects, integrated optomechanical information processing and open new avenues towards quantum optomechanics.
Finally, I will show how we recently use an ultrasensitive optical readout of monolayer TMD resonators to reveal their mechanical properties at cryogenic temperatures [6].
We find that the quality factor of monolayer WSe2 resonators greatly increases below room temperature, reaching values as high as 47000 at 4K, thus surpassing quality factor of monolayer graphene resonators with similar surface areas [7]. Optomechanics with atomically thin 2D semiconducting resonators remains an unexplored field of physics, which is interested in light-matter interactions in these systems and their nanomechanical response (ultra-cold resonators, weak forces probes). It is also a precious tool to better understand thermalization and mechanical damping processes within nano-objects. This type of experiments suggests the optical control of mechanical resonator vibrations and the calibration of optomechanical interaction at the single photon scale.

References
[1] Chan, J. et al. Laser cooling of a nanomechanical oscillator into its quantum ground state. Nature 478, 89–92 (2011).
[2] Teufel, J. D. et al. Sideband Cooling Micromechanical Motion to the Quantum Ground State. Nature 475, 13 (2011).
[3] Novoselov, K. S. et al. Electric field effect in atomically thin carbon films. Science 306, 666–9 (2004).
[4] Reserbat-Plantey, A., Marty, L., Arcizet, O., Bendiab, N. & Bouchiat, V. A local optical probe for measuring motion and stress in a nanoelectromechanical system. Nature Nanotechnology. 7, 151–5 (2012).
[5] Reserbat−Plantey A., Schädler K., Gaudreau L., Navickaite G., Güttinger J., Chang D.,Toninelli C., Bachtold A., and Koppens F. Electromechanical control of nitrogen−vacancy defect emission using graphene NEMS. Nature Communication. 7, 10218. (2016).
[6] Morell, N., Reserbat−Plantey, A., Tsioutsios, I., Schädler, K., Dubin, F., Koppens, F., Bachtold, A. High Quality Factor Mechanical Resonators Based on WSe2 Monolayers. Nano Letters. 16, 5102–5108. (2016)
[7] Bunch, J. S. et al. Electromechanical resonators from graphene sheets. Science 315, 490–3 (2007).

In this talk we will discuss the present status of theoretical studies and experimental searches performed in order to measure the di-Higgs process in various standard model (SM) final states. Furthermore, we will review the prospects of observing such channels at the 14 TeV high luminosity (HL) run of the large hadron collider (LHC). We will then discuss the prospects of observing certain non-standard final states in the di-Higgs category. Our focus will especially be on the scenario where one of the Higgs decays to a pair of $b$-jets and the other decays invisibly. We discuss the reach of the HL-LHC when (i) the production cross-section is exactly SM-like and (ii) when one includes a heavy scalar coupled to the top quarks and the SM Higgs. We will also review some other potential exotic final states.

Bi1-xSbx est classé comme un semi-métal de Dirac accidentel tridimensionnel à un niveau de dopage de x = 3% pour lequel une inversion de bande se produit. Lorsqu'un champ magnétique est appliqué parallèlement au courant dans les barres de Hall, le cône de Dirac dégénéré se divise en deux cônes de Weyl et on observe une magnétorésistance forte et négative comme l’indication de l'anomalie chirale.
Le semi-métal tridimensionnel de Dirac est idéalement adapté pour réaliser des états liés de Majorana dans des dispositifs hybrides supraconducteurs puisque la chiralité empêche la relation courant-phase 4π périodique d'ouvrir un intervalle à énergie nulle pour des états liés Andreev à incidence perpendiculaire. L'énergie de Fermi est intrinsèquement très proche du point de Dirac, ce qui assure moins de modes dans la jonction et augmente le poids du mode Majorana. Nous observons une forte contribution des états liés de Majorana 4π périodique au supercourant dans les dispositifs Nb- Bi1-xSbx -Nb. Les modes 4π sont révélés par l'étude de la jonction sous l'irradiation micro-ondes en GHz.