3D halide perovskites used in light emitters and PV systems exhibit an unusualanharmonicity, which is not accounted for in nowadays descriptions of phonons andelectron-phonon coupling. Therefore, the low frequency lattice vibrations andrelaxations were investigated in single crystals of the four 3D hybrid organoleadperovskites, MAPbBr3, FAPbBr3, MAPbI3, and FAPbI3, at the Brillouin zone centerusing Raman and Brillouin scattering and at the zone boundary using inelasticneutron scattering. The temperature dependence of the PbX6 lattice modes in thefour compounds can be renormalized into universal curves and no soft vibration isobserved excluding a displacive-like transitional dynamics related to structural phasetransitions. The reorientational (pseudospin) motions of the molecular cations exhibita seemingly order-disorder character recalling that of plastic crystals, but attributedto a secondary order-parameter. At ultra-low frequency, a quasi-elastic componentevidenced by Brillouin scattering and associated to the unresolved central peakobserved in neutron scattering, is attributed to center of mass anharmonic motionsand rattling of the molecular cations in the perovskite cavities. 3D halide perovskitesare therefore in a very unusual situation where anharmonicity prevails. It is leading topartial, extensive and ultraslow critical and stochatic dynamics connected or not tostructural instabilities. The extensive disorder of the lattice at normal operationtemperatures for devices is similar to premelting where only long-range acousticnormal modes survive.[1] A.Létoublon, S. Paofai, B. Ruffle, P. Bourges, B. Hehlen, T. Michel, C.Ecolivet, O.Durand, S. Cordier, C. Katan, J. Even. Elastic Constants, Optical Phonons andMolecular Relaxations in the High Temperature Plastic Phase of the CH3NH3PbBr3Hybrid Perovskite. J. Phys. Chem.Lett. 7, 3776 (2016)[2]C. Katan, A. D. Mohite, J. Even, Entropy in halide perovskites, Nature Materials,17, 377-379 (2018)[3]A. Ferreira, A. Létoublon, S. Paofai, S. Raymond, C. Ecolivet, B. Ruffle, S.Cordier, C. Katan, M. I. Saidaminov, A. A. Zhumekenov, O. M. Bakr, J. Even, P.Bourges, Elastic softness of hybrid lead halide perovskites, Phys. Rev. Lett., 121,085502 (2018)[4] A. Ferreira, S. Paofai, A. Létoublon, J. Ollivier, S. Raymond, B. Hehlen, B. Rufflé,S. Cordier, C. Katan, J. Even & P. Bourges, Direct evidence of weakly dispersed andstrongly anharmonic optical phonons in hybrid perovskites, Comm. Phys. 3, 48(2020).[5] B. Hehlen, P. Bourges, B. Rufflé, S. Clément, R. Vialla, A. C. Ferreira, C.Ecolivet, S. Paofai, S. Cordier, C. Katan, A. Létoublon, J. Even, Pseudospin-phononpretransitional dynamics in lead halide hybrid perovskites, Phys. Rev. B, 105,024306 (2022)

We study the heat transfer between N coupled quantum resonators with applied synthetic electric and magnetic fields realized by changing the resonator parameters by external drivings. To this end we develop two general methods, based on the quantum optical master equation and on the Langevin equation for N coupled oscillators where all quantum oscillators can have their own heat baths. The synthetic electric and magnetic fields are generated by a dynamical modulation of the oscillator resonance with a given phase. Using Floquet theory, we solve the dynamical equations with both methods, which allow us to determine the heat flux spectra and the transferred power. We apply these methods to study the specific case of a linear tight-binding chain of four quantum coupled resonators. We find that, in that case, in addition to a nonreciprocal heat flux spectrum already predicted in previous investigations, the synthetic fields induce here nonreciprocity in the total heat flux, hence realizing a net heat flux rectification.

Abstract Controlling the electrical properties of SiC requires knowledge of the nature and properties of extended defects. We have employed orthodox defect-selective etching and photo-etching methods to reveal typical and new structural defects in commercial SiC wafers. For photo-etching, the etch rate increases as the free carrier concentration decreases. The etch rate can be used to estimate the free carrier concentration with higher precision, and over a larger lateral and depth range than that accessed by Raman scattering. The logarithmic dependence of the etch rate on the free carrier concentration has been characterized.

The evaporation of drops of colloidal suspensions plays an important role in numerous contexts, such as the production of powdered dairies, the synthesis of functional supraparticles, and virus and bacteria survival in aerosols or drops on surfaces. The presence of colloidal particles in the evaporating drop eventually leads to the formation of a dense shell that may undergo a shape instability. Previousworks propose that, for drops evaporating very fast, the instability occurs when the particles form a rigid porous solid, constituted of permanently aggregated particles at random close packing. To date, however, no measurements could directly test this scenario and assess whether it also applies todrops drying at lower evaporation rates, severely limiting our understanding of this phenomenon and the possibility of harnessing it in applications. Here, we combine macroscopic imaging and spaceand time-resolved measurements of the microscopic dynamics of colloidal nanoparticles in drying drops sitting on a hydrophobic surface, measuring the evolution of the thickness of the shell and the spatial distribution and mobility of the nanoparticles. We find that, above a threshold evaporationrate, the drop undergoes successively two distinct shape instabilities, invagination and cracking. While permanent aggregation of nanoparticles accompanies the second instability, as hypothesized in previous works on fast-evaporating drops, we show that the first one results from a reversible glass transition of the shell, unreported so far. We rationalize our findings and discuss their implicationsin the framework of a unified state diagram for the drying of colloidal drops sitting on a hydrophobic surface.

Due to their atomically excellent structure and sp2-hybridization, carbon nanotubes (CNTs) have exceptional mechanical, thermal, and electrical properties. Single-walled CNTs (swCNTs) have recently gained interest as an intriguing host for the nanoscale confinement of fluids, with a variety of unexpected phenomena such as spontaneous filling, frictionless mass transport, unusual phase diagram etc[1]. The majority of these phenomena are still under debate and require experimental confirmation. However, it is challenging in this field to find experimental methods sensitive enough to carry out measurements at the level of individual nanotubes. The electronic properties of swCNTs are demonstrated to be sensitive to their diameter, defects, doping, adsorbates, and environment via swCNT field effect transistors (swCNT-FETs)[2], [3].In this contribution, we show that individual carbon nanotube field effect transistors (CNTFET) are the perfect tool for achieving this goal, enabling for the first time to accurate identification of water confined inside the nanotube. By investigating the electrical performances of several unopened and opened CNTFETs submitted to different atmosphere and temperature treatments, such as dry air, humidity, secondary vacuum, and current annealing, we demonstrate that it is possible to distinguish between water being outside and inside of the nanotube, just outside, or the nanotube free from water. Hence, we found that secondary vacuum and current annealing both shift the threshold gate voltage of opened swCNTs towards more negative values, however, the secondary vacuum had no effect on closed swCNTs compared to current annealing. In conclusion, the current annealing process is essential to distinguish water adsorbed outside from water confined inside swCNT. We demonstrate that this behavior is uniform across all devices’ metallicities, assuming that the nanotube’s surface has been pre-cleaned using current annealing. We will also discuss the mechanism behind the coupling of electronic transport and the presence of water.Our findings open up the possibility of using CNTFET to address long-standing issues in the nanofluidic community regarding the behavior of water confinement at the nanoscale, and also to use them for reliable, sensitive, and selective chemical and biological sensors.Reference:[1] T. A. Pascal, W. A. Goddard, and Y. Jung, “Entropy and the driving force for the filling of carbon nanotubes with water,” Proc. Natl. Acad. Sci., vol. 108, no. 29, pp. 11794–11798, 2011, doi: 10.1073/pnas.1108073108.[2] D. Cao et al., “Electronic sensitivity of carbon nanotubes to internal water wetting,” ACS Nano, vol. 5, no. 4, pp. 3113–3119, 2011, DOI: 10.1021/nn200251z.[3] I. Heller, A. M. Janssens, J. Männik, E. D. Minot, S. G. Lemay, and C. Dekker, “Identifying the mechanism of biosensing with carbon nanotube transistors,” Nano Lett., vol. 8, no. 2, pp. 591–595, 2008, DOI: 10.1021/nl072996i.