Istituto Officina dei Materiali

CeTe3 is a 2-dimensional (2D) Van der Waals (VdW) material with incommensurate charge density waves (CDW), extremely high transition temperature (TCDW), and a large momentum-dependent CDW gap that leaves a significant portion of the Fermi surface intact. It is also considered to be a weak Kondo system, a property unexpected for a material with incommensurate CDW, where each atomic site is slightly different. Here, we study the properties of the CDW state in several RTe3 (R is rare earth) materials and examine the hybridization of itinerant states with the localized Ce 4f multiplet in CeTe3 by using angle resolved photoemission spectroscopy. We find that the renormalization of the itinerant states originating from the hybridization with the deeper localized 4f states at −260 meV is k−dependent and extends to the Fermi level. As these localized states are far from the Fermi level, the observed hybridization affects the effective masses only marginally and does not lead to heavy fermions. However, since the same renormalizing mechanism normally leads to the heavy fermion physics when the localized 4f states are near the Fermi level, our observation of its strong k−dependence suggests that this could be the reason for discrepancy between the heavy masses in specific heat and light ones in Shubnikov de Haas oscillations, often observed in heavy fermions.

ABSTRACT In analogy to their solid‐state counterparts, optical beams endowed with skyrmionic textures of the Stokes vector have recently garnered increasing attention due to their inherent topological protection and unique polarization structure. Despite significant advancements in research and applications, optical skyrmions still lack compact optical solutions for their versatile generation and control. This study presents the design, fabrication, and experimental validation of dual‐functional metaoptics for the customized generation and reconfigurability of skyrmionic patterns of light. By leveraging complex light manipulation at the nanoscale, dielectric metasurfaces composed of anisotropic meta‐atoms enable the simultaneous and asymmetric shaping of orthogonal polarization states using a single optical element, thereby achieving the generation of full Poincaré beams with skyrmionic topology of the Stokes vector. Furthermore, we demonstrate the dynamic tuning and reconfigurability of the skyrmionic state and order through precise wavefront engineering and polarization control. This research introduces a novel framework for flexible reconfiguration and manipulation of Stokes skyrmions, establishing the foundation for their practical integration across a diverse range of emerging information and communication technologies, potentially revolutionizing the exploitation of information resilience in photonics and optoelectronics.

The vibrational circular dichroism (VCD) spectra of (R)-2-chloromethyl-oxirane and (R)-2-chloromethyl-thiirane have been recorded in a vast spectral region including mid-IR, CH-stretching fundamentals and bending-CC/CO(CS) overtone/combination regions in the mid-IR, and CH-stretching overtone/combination regions in the near infrared (NIR). The presence of sulfur is associated with intensification of the NIR-VCD spectra, similarly to what is monitored with electronic circular dichroism (ECD) and optical rotatory dispersion (ORD). DFT calculations, dealing with anharmonicity at the GVPT2 level or based on the local mode approximation, permit to correctly predict the large majority of observed VCD and IR/NIR bands and to explain the role of various molecular moieties. Also, ORD data are better interpreted by including anharmonic vibrational contributions.

The dielectric response of amorphous organic solids at the timescale of atomic motion has broad implications for their photophysics, governing spectroscopic properties and excited-state relaxation, among other phenomena. We present an original approach to the calculation of the vibrational contribution to the frequency-dependent dielectric permittivity. Our methodology, combining molecular dynamics simulations, density functional theory calculations, and linear response theory, is applied to a set of amorphous carbazole-based small-molecule matrices, widely used as host materials in organic light-emitting diodes. Our analysis reveals the crucial role of hindered molecular rotations (librations) in the solid-state matrices of dipolar compounds. These modes manifest in the very-low frequency ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mo>&lt;</a:mo> <a:mn>100</a:mn> <a:mspace width="0.28em"/> <a:msup> <a:mrow> <a:mi>cm</a:mi> </a:mrow> <a:mrow> <a:mo>−</a:mo> <a:mn>1</a:mn> </a:mrow> </a:msup> </a:mrow> </a:math> ) region of the dielectric function, accounting for up to one-third of the total vibrational contribution to the static dielectric constant in a dipolar compound like 3,3'-di(carbazol-9-yl)-5-cyano-1,1'-biphenyl. This low-frequency contribution is found to be crucial for determining the variations in the static dielectric constant across various materials.

The manipulation of light through its interactions with artificially structured media is a cornerstone of photonics. The rescaling of this concept to the X-ray realm-which will enable us to control X-ray light with the same precision routinely available in the visible/IR range-has so far been hindered by the inherent difficulty of realizing photonic structures with the sub-nanometric resolution dictated by X-ray wavelengths. A promising approach to this challenge is based on the so-called Berry-phase effect, the large beam translations undergone by X-ray photons propagating in a deformed crystal, due to the simultaneous presence of Berry curvatures in real and reciprocal space. In this work, the controlled crystal distortions required to rein in this effect are obtained by pairing the lattice expansion observed upon H irradiation of GaAsN with a spatially selective hydrogenation technique. The macroscopic beam translations measured here are striking manifestations of the Berry curvatures associated with the sub-nanometric lattice distortions induced by H incorporation. Through the comparison with a dedicated theoretical model, the individual translation branches observed in X-ray transmission can be traced back to specific deformation features present within the samples, establishing a predictive framework for the control of X-ray propagation in the fabricated structures.

Bio-hybrid actuators (BHAs) integrate biological components, such as skeletal muscle cells, with synthetic materials to generate motion through external stimuli. Here, we study the use of light to remotely control 3D bio-hybrid actuators. Specifically, the employment of the amphiphilic azobenzene derivative Ziapin2 to modulate cell membrane capacitance and induce contraction has been proved to be effective for myotube in 2D planar substrates. Transitioning from 2D planar substrates to 3D scaffolds demands the full characterization of the interaction of light with the cell seeded scaffold. Scattering analysis, confocal microscopy, and time-resolved photoluminescence (TRPL) have been effectively used to investigate and model light interaction of these 3D structures. The application of these techniques allowed us to optimize sample preparation and quantitative study the behavior, in a non-destructive way, on this new class of biomaterials. This study aims at establishing a foundation for the characterization of scalable, optically controlled 3D bio-hybrid actuators with applications in soft robotics and implantable biomedical device.

Light-induced metastable phases are exotic, long-lived out-of-equilibrium states of matter. Optical control offers a powerful approach to engineering these phases, enabling dynamic tuning of their electronic and structural properties. Using time- and angle-resolved photoemission spectroscopy, we investigate the emergence of a metastable phase induced by a strong infrared pump in the charge-density-wave (CDW)-Mott insulator 1 T − TaS 2 . Furthermore, we demonstrate how its properties can be optically manipulated by varying the photoexcitation strength. A long-lived stabilization of the renormalized electronic band structure serves as a signature of the metastable phase. It displays a relaxed periodic lattice distortion (PLD) and primarily lattice-driven dynamics. The emergence of a new dispersive band in the vicinity of the Hubbard bands reveals the formation of a novel band structure unique to the metastable phase. Our pump-fluence-dependent studies reveal a threshold (incident) fluence F C ∼ 1.3 mJ / cm 2 for inducing the metastable phase, above which the band renormalization continuously evolves with increasing fluence. For F ⩽ 3.4 mJ / cm 2 , stronger photoexcitation progressively drives the phase to higher energies, accompanied by a more relaxed PLD and reduced CDW amplitude. The properties of the metastable phase are strongly influenced by the transient dynamics at each fluence, and the associated fast timescales suggest that the intrinsic CDW amplitude mode remains unaffected by optical manipulation. These findings highlight the potential of optical control in tuning the properties of metastable phases in quantum materials, offering new insights into the manipulation of CDW systems and paving the way for future investigations in nonequilibrium phase engineering.

In this contribution, we report the effect of two anions with different degrees of hydration, namely sulphate (SO42-) and chloride (Cl-), on the gelation of a low hydrophobic agarose (residual methylation=7.4%). Using a combined approach of oscillatory rheology, low-field NMR, small-angle X-ray scattering (SAXS) and cryo-SEM, we propose that the addition of anions affects water molecules around agarose, causing general dehydration of the biopolymer. This results in earlier temperature of gelation, Tgel, less water-biopolymer interactions and greater elasticity of the network at the end of the gelation stage. Mechanical differences level off at the end of the pseudo-equilibrium stage, that is, after 24h of incubation of the hydrogels at T=37°C. This causes also low sensitivity of the hydrogels to high ionic strength, which can be explained mainly by the residual amounts of hydrophobic domains of the agarose used in this study. In addition, this contribution provides insights into the role of the agarose concentration, Cp, during the gelation stage. We demonstrate that the established correlation between Cp, network elasticity, and Tgel can be related to the extent of interactions between water and agarose. Finally, we discuss the mechanical stimulation of agarose during the gelation stage in the presence of the highly hydrated SO42- anion. We report that increasing the oscillatory strain during temperature sweep experiments has negligible effects on Tgel, but alters the evolution of the storage modulus on cooling.

Pioneering a novel integrated photonic platform, Brillouin–Raman Microspectroscopy on‐a‐Chip is presented, which enables real‐time, high resolution analysis of mechano‐chemical dynamics in complex 3D biological systems under controlled deformation. This contact‐free, all‐optical method seamlessly combines Brillouin and Raman microscopy within microfluidic devices, providing a unique correlative approach to overcome current limitations in probing cellular mechanics and biochemical responses in live multicellular models. This innovative platform, when applied to breast tumor spheroids, revealed that rapid, cyclical mechanical deformations, mimicking in vivo stresses, profoundly impacts tumor physiology. These findings demonstrate that controlled deformations trigger rapid nuclear shape changes and robust transcriptional reprogramming, marked by a significant (48‐fold) upregulation of the early stress response regulator ATF3. These responses are accompanied by global spheroid stiffening, as precisely quantified by Brillouin spectroscopy. Remarkably, repeated deformation imprints a form of mechanical memory in these collective systems, which culminates in enhanced collagen invasion over 24 h. The label‐free methodology sets a new benchmark in biophotonics, unlocking a new class of experiments to probe and modulate physiological and pathological processes with transformative potential for cancer research, broader mechanobiology, and the study of mechanical memory in organoids and other complex 3D models.