Many important processes in chemistry and biology occur at interfaces where the molecular interactions and dynamics significantly differ from those observed in the bulk. Proper characterization of the behavior of peptides and proteins at macromolecular interfaces, including their reversible adsorption to surfaces and their folding into the membrane, is a prerequisite for understanding fundamental physiological processes stemming from intracellular reactions. A powerful noninvasive, optical, surface analytical tool is vibrational sum frequency generation (VSFG) spectroscopy, which often enables direct observation of the structural and dynamical properties of interfacial molecules. Nevertheless, the acquisition times and spectral resolution of traditional broadband VSFG spectrometers are far from ideal to follow the interaction of macromolecules at bio-interfaces in real-time and in situ. In my talk, I will provide an overview of our mid-IR light sources integrated into our unique high-resolution LF0-kHz VSFG spectrometer. By employing such a spectrometer, the collection of vibrational spectra of biologically relevant macromolecules at air-solid, air-liquid, and buried interfaces has become possible at an unprecedented combination of signal-to-noise ratios, acquisition times, and spectral resolution in the spectral range of 770-3800 cm-1. I will present examples of in situ peptide and protein folding at model cell membranes and a model system for studying protein-protein interactions or even enzymatic reactions.

In 2022, the CNRS Institute of Physics (now CNRS-Physics) commissioned G. Debregeas and myself to write a text on the impact of the ecological, energy and digital transitions on research in the laboratories (sobriety). This text would then be used for the CNRS-Physics 2030 outlook. So we set up a bureau with, in addition to G. Debregeas and myself, Laëtitia Marty (I. Neel), Delphine Debarre (Liphy), Guillaume Roux (LPTMS), Sylvain Capponi (LPT Toulouse) and Christophe Arnold (Gemac - Versailles) for a group made up of researchers, teachers and research support staff. The idea was also to try to involve the community as much as possible in this work. So I propose to present the approach we have chosen. I will then outline the 12-page text we produced in July 2023, which concerns changes in our profession that we think will be important in the medium term. Finally, I’d like to conclude with a discussion of the approach underway in my laboratory, the INSP, for shorter-term actions aimed at trying to reduce our laboratory’s Carbon Footprint. This talk will be followed by a discussion on this topic led by the Labo 1.5 team.

Distinguishing edited cells from non-edited/off-target edits would transform the manufacturing of cell editing products. Visualizing the separation of bacterial colony function would open up our fundamental understanding of microbiology. Identifying chemical cues in pap smear results before the appearance of cells with odd morphologies could lead to earlier identification of dysplasia, improving patient outcomes and treatment options. In short, imaging the dynamic chemical landscape within cells and tissues would revolutionize biological discovery and medicine. Molecular vibrational imaging techniques detect the small oscillations between bonded atoms, providing dense spectral information about composition and state without the addition of fluorophores or dyes. Technologies, such as Raman and infrared microscopies, have offered this capability for over half a century, but significant limitations in speed, resolution, or sample preparation have prevented their ubiquity. In this presentation, I will present our developments at NIST of broadband coherent anti-Stokes Raman scattering (BCARS), a coherent Raman imaging method with an unprecedented combination of speed, sensitivity, and spectral breadth; and our development of IR microscopy for live-cell imaging, which is enabling time-course IR imaging of cell cultures at the benchtop rather than synchrotron sources.

The paper reviews experimental and theoretical studies on polarized terahertz radiation-induced photocurrents in graphene and graphene-based 2D materials. We consider the optoelectrical phenomena excited by THz radiation in graphene and twisted graphene and present the state of the art in this field, including both recent advances and well-established results, see e.g. [1-7]. Different physical mechanisms of the THz radiation excited dc currents proportional to the second powers of the radiation electric field are presented, including phenomenological description based on symmetry arguments, models visualizing the physics of nonlinear responses, and microscopic theory of several phenomena. The following effects yielding a dc current proportional to the square of the irradiation electric field are discussed: high-frequency Hall effect at zero magnetic field, edge photogalvanic effects, ratchet effects in graphene with lateral superlattices, cyclotron resonance (CR) assisted dc currents, terahertz induced magnetooscillations coupled to the CR harmonics, Bernstein modes, as well as multiple oscillations upon variation of the gate voltage in twisted bilayer graphene near the second magic angle. We show that nonlinear transport opens up new possibilities for probing Dirac electrons. [1] S.D. Ganichev et al, Annalen der Physik 529, 1600406 (2017) [2] M.M. Glazov et al, Physic Reports 535, LF1, (2014) [3] M. Otteneder et al, Nano Lett. 20, 7152 (2020) [4] E. Mönch et al, Nano Lett. 20, 5943 (2020) [5] D. A. Bandurin et al, Nature Physics 18, 462 (2022) [6] S. Candussio et al, Phys. Rev. B LF3, 125408 (2021) [7] E. Mönch et al, Phys. Rev. B LF7, 115408 (2023)

Self-assembly is both an advantageously spontaneous process to organize molecular or colloidal entities into functional superstructures and a key-feature of how life builds its components. However, compared to their living counterparts, synthetic materials made by self-assembly usually lack some of the interesting properties of living systems such as multicomponent character or capability to adapt, transform and evolve. In this presentation, I will describe different systems where life-like properties can emerge from self-assembled synthetic materials. First, I will show that user-defined and elaborate nanostructures (e.g., DNA origamis, nanogrids, SST assemblies) can be obtained by the isothermal self-assembly of hundreds of different DNA bricks and proteins with a unique capability to optimize, adapt, evolve and even completely transform their morphology, either spontaneously or under command [1-2]. I will also present a new DNA self-assembly principle that does not rely on base-pairing principles, showing in particular that photosensitive DNA intercalating molecules can co-assemble with DNA bases to form new extended supramolecular materials with intriguing dynamic properties. I will describe in particular the formation of photoswitchable 3D crystals with unique photoreversible growth and light-gated fluorescence [3]. Finally, I will present different colloidal self-assembly processes at air-water or liquid-liquid interfaces and explore how dynamic properties can emerge from such systems. Starting from the familiar situation of drying drop containing a colloidal suspensions, we have been interested in controlling/cancelling the so-called “coffee-ring effect” [4-7] or turning it into a low-cost yet powerful medical diagnostic tool [8]. In such systems, however, particles adsorb at the interface to form amorphous structures. This led us to invent a simple method in which bulk particles adsorb at the water-interface and directly crystallize there. Based on the use of ultralow amounts of surfactant, 2D colloidal crystals spontaneously form without any other applied force than their own weight [9]. This method allows us to crystallize a broad variety of nanometric and micrometric particles, including those made of polymers, metals or inorganic materials, and tune the characteristics of the colloidal crystals [LF] that can be further deposited on solid substrates [11]. These colloidal crystals display intense structural colors as well as, under some conditions, some remarkable dynamic properties at the air/water interface. For instance, using light, we can reversibly melt/crystallize these colloidal assemblies on command, evidencing other life-like properties, such as dissipative character or living crystallization [12-CR]. [1] Rossi-Gendron et al., Nat. Nanotechnol. 2023, 18, CR11–CR18 [2] Nakazawa et al., Angew. Chem. Int. Ed. 2021, 60, 15214 –15219 [3] Zhou et al., J. Am. Chem. Soc. 2019, 141, 9321–9329 [4] Anyfantakis et al., Angew. Chem. Int. Ed. 2014, 53, 14077–14081 [5] Varanakkottu et al., Nano Lett. 2016, 16, 644–650 [6] Poulichet et al., J. Colloid. Interf. Sci. 2020, 573, 370-375 [7] Galy et al., ACS Appl. Mater. Interfaces 2022, 14, 3374–3384 [8] Devineau et al., J. Am. Chem. Soc. 2016, CR8, 11623–11632 [9] Anyfantakis, Langmuir 2018, 34, 15526−15536 [LF] Vialetto et al., Nanoscale 2020, 12, 6279-6284 [11] Vialetto et al., Adv. Sci. 2024, 11, 2307893 [12] Vialetto et al. Angew. Chem. Int. Ed. 2019, 58, 9145-9149 [CR] Vialetto et al., J. Am. Chem. Soc. 2021, 143, 11535−11543

Nearly twenty years ago in an experiment at Brookhaven National Laboratory, physicists measured the muon's anomalous magnetic moment, a_mu, with a remarkable precision of 0.54 parts per million. Since that time, the reference Standard Model prediction for a_mu has exhibited a discrepancy with experiment of over 3 standard deviations, raising the tantalizing possibility of elementary particles or fundamental forces as yet undiscovered. On April 7, 2021 the physicists of an ongoing experiment at Fermilab presented first results of a new measurement of a_mu, brilliantly confirming Brookhaven's measurement and bringing the discrepancy with the reference prediction to a near discovery level of 4.2 sigma. This discrepancy was further enhanced to 5.1 sigma this past with the publication of Fermilab’s new result that reduces the measurement uncertainty by a factor of 2. According to usual particle physics standards, such a discrepancy would mean that new fundamental physics has been uncovered. In the meantime a very large-scale supercomputer calculation of the contribution that most limits the precision of the Standard Model prediction was performed by the Budapest-Marseille-Wuppertal collaboration. The results of this lattice quantum chromodynamics (QCD) calculation paint a very different picture, in particular reducing the difference between theory and experiment and suggesting that new physics may not be needed to explain the current, experimental, world-average value of a_mu. However, it does so at the expense of an untenable discrepancy with the data-driven determination of this most uncertain contribution. After an introduction and a discussion of the current experimental and theoretical status of a_mu, I will present this precise lattice QCD calculation and partial confirmations by other teams. I will also present a framework that enables a comparison of the primary ingredients that are used in the lattice QCD and data-driven approaches and discuss the steps that are required to make a Standard Model prediction that will allow determine whether the final results of the Fermilab experiment, expected in 2025, indicate the presence of new fundamental physics.

A remarkable success of 20th-century Physics is the framework of statistical Physics that bridges the atomistic and macroscopic worlds. However, this framework is only limited to systems in thermal equilibrium. In reality, most systems in nature are outside equilibrium. A cup of coffee left on a table, reaches thermal equilibrium in an hour or so by releasing heat, but over longer periods it evaporates. Living matter, like bacteria, generates energy currents from burning ATP to self-organize at large scales. Such non-zero currents break time-reversal symmetry, thus constantly generating entropy. As a result, the statistics of these systems do not follow the principals of statistical Physics. In fact, at present, there is no general conceptual framework à la Gibbs-Boltzmann to describe non-equilibrium Physics from first principles. It is not even clear how to generalize the basic ideas of state variables like pressure and temperature, or thermodynamic potentials like the free energy. An emerging idea is to build a unifying theory at a mesoscopic scale, similar to the Landau-Ginzburg theory for equilibrium fluctuations. I will discuss, how the theory of large deviations offers such an avenue by extending the idea of the Landau free energy outside equilibrium in terms of large deviation functions. This way, non-equilibrium phase transitions appear as singularities in large deviations, as in equilibrium; generic non-local response of non-equilibrium states is a simple consequence of non-local large deviation functions, and fluctuation relations are due to symmetries of large-deviations. Many important recent advances in non-equilibrium Physics came from this large deviation approach, driven by experiments, computer simulations, and theoretical analysis of minimal models. In this talk, I will review these new ideas and illustrate them with examples from soft-condensed matter. These include anomalous tracer diffusion in single-file motion, dynamical phase transitions in stochastic processes, thermodynamic uncertainty relations, and hydrodynamics of classical and quantum transport.

The rheology of concentrated non-Brownian suspensions has undergone a small revolution in the last 15 years when the importance of the role played by solid contacts between particles was realized. Considering these contacts has allowed to explain the continuous or discontinuous shear-thickening in dense suspensions [1] and, more recently, the shear-thinning observed beyond the shear-thickening transition [2], i.e. in frictional non-Brownian suspensions [3]. I will start by presenting a number of questions about suspension dynamics that would remain unanswered if we didn't take particle-to-particle contact into account. I will then focus on shear thinning to show that the decrease in viscosity recorded as shear stress increases can be explained by the variable friction between particles [4]. To this aim, I will first show how the study of the microstructure of suspensions under shear has revealed the existence of solid contacts between particles and that they are made possible by the presence of roughness on the particle surface. I will then present some numerical results that show how solid friction between particles increases the viscosity of suspensions, and how modelling inter-particle contact by an elasto-plastic mono-contact gives a very good account of the shear-thinning observed in concentrated non-Brownian suspensions. I will conclude by presenting measurements of the friction coefficient between two particles using an AFM [4], which clearly validate this scenario and highlight the close links between the microscopic friction properties of the particles and the macroscopic rheological behaviour of suspensions. [1] R. Mari, R. Seto, J.F. Morris and M.M. Denn, J. Rheol., 2014, 58(6), 1693-1724. [2] G. Chatté, J. Comtet, A. Niguès, L. Bocquet, A. Siria, G. Ducouret, F. Lequeux, N. Lenoir, G. Ovarlez and A. Colin, Soft Matter, 2018, 14(6), 879-893. [3] L. Lobry, E. Lemaire, F. Blanc, S. Gallier and F. Peters, J. Fluid Mech., 2019, 860, 682-7LF. [4] M. Arshad, A. Maali, C. Claudet, L. Lobry, F. Peters and E. Lemaire, Soft Matter, 2021, 17(25), 6088-6097.