Collisions of Self-Bound Quantum Droplets.

We report on the study of binary collisions between quantum droplets formed by an attractive mixture of ultracold atoms. We distinguish two main outcomes of the collision, i.e., merging and separation, depending on the velocity of the colliding pair. The critical velocity v_{c} that discriminates between the two cases displays a different dependence on the atom number N for small and large droplets. By comparing our experimental results with numerical simulations, we show that the nonmonotonic behavior of v_{c}(N) is due to the crossover from a compressible to an incompressible regime, where the collisional dynamics is governed by different energy scales, i.e., the droplet binding energy and the surface tension. These results also provide the first evidence of the liquidlike nature of quantum droplets in the large N limit, where their behavior closely resembles that of classical liquid droplets.

Velocity dependence of sliding friction on a crystalline surface.

We introduce and study a minimal 1D model for the simulation of dynamic friction and dissipation at the atomic scale. This model consists of a point mass (slider) that moves over and interacts weakly with a linear chain of particles interconnected by springs, representing a crystalline substrate. This interaction converts a part of the kinetic energy of the slider into phonon waves in the substrate. As a result, the slider experiences a friction force. As a function of the slider speed, we observe dissipation peaks at specific values of the slider speed, whose nature we understand by means of a Fourier analysis of the excited phonon modes. By relating the phonon phase velocities with the slider velocity, we obtain an equation whose solutions predict which phonons are being excited by the slider moving at a given speed.

Primary cortical neurons on PMCS TiO2 films towards bio-hybrid memristive device: A morpho-functional study.

We report a comprehensive study of the biocompatibility and neurocompatibility of titanium dioxide films (TiO2) prepared by Pulsed Microplasma Cluster Source (PMCS). This technique uses supersonic pulsed beams seeded by clusters of the metal oxide synthesized in a plasma discharge. The final stoichiometry of the TiO2 thin films is tuned changing the gas mixture, achieving stoichiometric or oxygen overstoichiometric films. All the films showed consistent biocompatibility and a spontaneous absorption of poly-d-lysine (PDL) that favors the adhesion and growth of murine cortical neurons. Moreover, the bioelectrical activity of the neuronal culture grown on the TiO2 film can be modulated by changing the chemistry of the surface. This work paves the way to develop a bio-hybrid neuromorphic device, where viable nerve cells are grown directly over a titanium dioxide film showing a network of memristors.