Electron Glass Phase with Resilient Zhang-Rice Singlets in LiCu_{3}O_{3}.

LiCu_{3}O_{3} is an antiferromagnetic mixed valence cuprate where trilayers of edge-sharing Cu(II)O (3d^{9}) are sandwiched in between planes of Cu(I) (3d^{10}) ions, with Li stochastically substituting Cu(II). Angle-resolved photoemission spectroscopy (ARPES) and density functional theory reveal two insulating electronic subsystems that are segregated in spite of sharing common oxygen atoms: a Cu d_{z^{2}}/O p_{z} derived valence band (VB) dispersing on the Cu(I) plane, and a Cu 3d_{x^{2}-y^{2}}/O 2p_{x,y} derived Zhang-Rice singlet (ZRS) band dispersing on the Cu(II)O planes. First-principle analysis shows the Li substitution to stabilize the insulating ground state, but only if antiferromagnetic correlations are present. Li further induces substitutional disorder and a 2D electron glass behavior in charge transport, reflected in a large 530 meV Coulomb gap and a linear suppression of VB spectral weight at E_{F} that is observed by ARPES. Surprisingly, the disorder leaves the Cu(II)-derived ZRS largely unaffected. This indicates a local segregation of Li and Cu atoms onto the two separate corner-sharing Cu(II)O_{2} sub-lattices of the edge-sharing Cu(II)O planes, and highlights the ubiquitous resilience of the entangled two hole ZRS entity against impurity scattering.

Flat Γ Moiré Bands in Twisted Bilayer WSe_{2}.

The recent observation of correlated phases in transition metal dichalcogenide moiré systems at integer and fractional filling promises new insight into metal-insulator transitions and the unusual states of matter that can emerge near such transitions. Here, we combine real- and momentum-space mapping techniques to study moiré superlattice effects in 57.4° twisted WSe_{2} (tWSe_{2}). Our data reveal a split-off flat band that derives from the monolayer Γ states. Using advanced data analysis, we directly quantify the moiré potential from our data. We further demonstrate that the global valence band maximum in tWSe_{2} is close in energy to this flat band but derives from the monolayer K states which show weaker superlattice effects. These results constrain theoretical models and open the perspective that Γ-valley flat bands might be involved in the correlated physics of twisted WSe_{2}.

Fate of Quasiparticles at High Temperature in the Correlated Metal Sr_{2}RuO_{4}.

We study the temperature evolution of quasiparticles in the correlated metal Sr_{2}RuO_{4}. Our angle resolved photoemission data show that quasiparticles persist up to temperatures above 200 K, far beyond the Fermi liquid regime. Extracting the quasiparticle self-energy, we demonstrate that the quasiparticle residue Z increases with increasing temperature. Quasiparticles eventually disappear on approaching the bad metal state of Sr_{2}RuO_{4} not by losing weight but via excessive broadening from super-Planckian scattering. We further show that the Fermi surface of Sr_{2}RuO_{4}-defined as the loci where the spectral function peaks-deflates with increasing temperature. These findings are in semiquantitative agreement with dynamical mean field theory calculations.

Light-Induced Renormalization of the Dirac Quasiparticles in the Nodal-Line Semimetal ZrSiSe.

In nodal-line semimetals, linearly dispersing states form Dirac loops in the reciprocal space with a high degree of electron-hole symmetry and a reduced density of states near the Fermi level. The result is reduced electronic screening and enhanced correlations between Dirac quasiparticles. Here we investigate the electronic structure of ZrSiSe, by combining time- and angle-resolved photoelectron spectroscopy with ab initio density functional theory (DFT) complemented by an extended Hubbard model (DFT+U+V) and by time-dependent DFT+U+V. We show that electronic correlations are reduced on an ultrashort timescale by optical excitation of high-energy electrons-hole pairs, which transiently screen the Coulomb interaction. Our findings demonstrate an all-optical method for engineering the band structure of a quantum material.

Evidence of Large Polarons in Photoemission Band Mapping of the Perovskite Semiconductor CsPbBr_{3}.

Lead-halide perovskite (LHP) semiconductors are emergent optoelectronic materials with outstanding transport properties which are not yet fully understood. We find signatures of large polaron formation in the electronic structure of the inorganic LHP CsPbBr_{3} by means of angle-resolved photoelectron spectroscopy. The experimental valence band dispersion shows a hole effective mass of 0.26±0.02 m_{e}, 50% heavier than the bare mass m_{0}=0.17 m_{e} predicted by density functional theory. Calculations of the electron-phonon coupling indicate that phonon dressing of the carriers mainly occurs via distortions of the Pb-Br bond with a Fröhlich coupling parameter α=1.81. A good agreement with our experimental data is obtained within the Feynman polaron model, validating a viable theoretical method to predict the carrier effective mass of LHPs ab initio.

Radial Spin Texture of the Weyl Fermions in Chiral Tellurium.

Trigonal tellurium, a small-gap semiconductor with pronounced magneto-electric and magneto-optical responses, is among the simplest realizations of a chiral crystal. We have studied by spin- and angle-resolved photoelectron spectroscopy its unconventional electronic structure and unique spin texture. We identify Kramers-Weyl, composite, and accordionlike Weyl fermions, so far only predicted by theory, and show that the spin polarization is parallel to the wave vector along the lines in k space connecting high-symmetry points. Our results clarify the symmetries that enforce such spin texture in a chiral crystal, thus bringing new insight in the formation of a spin vectorial field more complex than the previously proposed hedgehog configuration. Our findings thus pave the way to a classification scheme for these exotic spin textures and their search in chiral crystals.

Facial growth and morphology of cleft lip and/or palate patients after corrective surgery according to P.I.S.A. technique.

Cleft lip and/or palate patients (CLP) undergo corrective surgery that can affect facial growth. The aim of this study was to analyze facial growth and maxillary development of CLP subjects after surgery according to P.I.S.A. technique (Peri osteoplasty Improves Symmetry and Aesthetic). Cephalometric tracings of 55 patients were performed, thirty-three of which belonged to the test group, while the lasting twenty subjects were part of the control group. The test group was formed by cleft lip and/or palate patients after surgical repair according to P.I.S.A. technique. The control group included patients unaffected by this malformation, with an Angle's first class, selected from the Michigan Growth Study sample. Facial growth and upper maxilla development analysis was carried out by comparing the data obtained from the cephalometric traces of cleft patients who performed an early surgery, with the values of the same parameters measured in non-cleft subjects, providing the normal values. The results of this study showed, in the test group, a maxillary and mandibular bi-retrusion, a more negative facial convexity, the absence of a marked discrepancy in the skeletal relationships, a slight tendency towards hyper-divergence. .

Towards an in situ, full-power gauge of the focal-volume intensity of petawatt-class lasers.

About 50 years ago, Sarachick and Schappert [Phys. Rev. D. 1, 2738-2752 (1970)] showed that relativistic Thomson scattering leads to wavelength shifts that are proportional to the laser intensity. About 28 years later, Chen et al. [Nature 396, 653-655 (1998)] used these shifts to estimate their laser intensity near 1018 W/cm 2. More recently, there have been several theoretical studies aimed at exploiting nonlinear Thomson scattering as a tool for direct measurement of intensities well into the relativistic regime. We present the first quantitative study of this approach for intensities between 1018 and 1019 W/cm 2. We show that the spectral shifts are in reasonable agreement with estimates of the peak intensity extracted from images of the focal area obtained at reduced power. Finally, we discuss the viability of the approach, its range of usefulness and how it might be extended to gauge intensities well in excess of 1019 W/cm 2.

Trichinella spiralis in a South American sea lion (Otaria flavescens) from Patagonia, Argentina.

Trichinella spp. from a sylvatic cycle has been found in several animal species such as pumas (Puma concolor), armadillos (Chaetophractus villosus), rats (Rattus norvegicus), and wild boars (Sus scrofa) in Argentina. Moreover, Trichinella infection has been detected in a wide range of marine mammals around the world, including polar bears (Ursus maritimus) and walruses (Odobenus rosmarus). Until the present time, Trichinella spp. infection has not been detected in marine mammals of South America. Samples from four South American sea lions (Otaria flavescens) found dead in Rio Negro, Argentina, were analyzed by artificial digestion, and in the case of one animal, Trichinella larvae were identified at the species level by nested multiplex PCR as Trichinella spiralis. This is the first report of a Trichinella species infecting marine mammals from South America.

Publisher's Note: Electronic Phase Separation and Dramatic Inverse Band Renormalization in the Mixed-Valence Cuprate LiCu_{2}O_{2} [Phys. Rev. Lett. 118, 176404 (2017)].

This corrects the article DOI: 10.1103/PhysRevLett.118.176404.

Electronic Phase Separation and Dramatic Inverse Band Renormalization in the Mixed-Valence Cuprate LiCu_{2}O_{2}.

We measured, by angle-resolved photoemission spectroscopy, the electronic structure of LiCu_{2}O_{2}, a mixed-valence cuprate where planes of Cu(I) (3d^{10}) ions are sandwiched between layers containing one-dimensional edge-sharing Cu(II) (3d^{9}) chains. We find that the Cu(I)- and Cu(II)-derived electronic states form separate electronic subsystems, in spite of being coupled by bridging O ions. The valence band, of the Cu(I) character, disperses within the charge-transfer gap of the strongly correlated Cu(II) states, displaying an unprecedented 250% broadening of the bandwidth with respect to the predictions of density functional theory. Our observation is at odds with the widely accepted tenet of many-body theory that correlation effects generally yield narrower bands and larger electron masses and suggests that present-day electronic structure techniques provide an intrinsically inappropriate description of ligand-to-d hybridizations in late transition metal oxides.

The influence of particle size of amino-functionalized MCM-41 silicas on CO2 adsorption.

The CO2 adsorption properties of hybrid organic-inorganic MCM-41 silicas with different particle sizes are described here. Micrometric to nanometric MCM-41 silicas are functionalized by introducing amino groups via grafting of 3-[2-(2-aminoethyl)aminoethyl]aminopropyltrimethoxysilane (PAPTS). A combination of FTIR and SS-NMR spectroscopies is adopted to distinguish between physisorbed and chemisorbed CO2. A higher amount of CO2 is physisorbed in the nanometric sample because of a higher pore volume, whereas chemisorbed (carbamate and acid carbamic) species are more abundant in the micrometric sample. The adsorption process is also quantitatively studied using three different techniques (i.e. volumetric measurements, Thermo-Gravimetric Analysis (TGA) and Zero Length Column (ZLC) analysis), especially focusing on the reversibility of the reactions between CO2 and amino groups. The three techniques show a higher CO2 adsorption capacity for MCM-41 with nanometric size compared to the micrometric one. Finally, the process is studied at different temperatures (i.e. from 35 to 90 °C) in order to find the best operating conditions.

CO2 adsorption on different organo-modified SBA-15 silicas: a multidisciplinary study on the effects of basic surface groups.

Hybrid organic-inorganic SBA-15 silicas functionalized with increasing amounts of amino groups were studied in this work aiming to evaluate the effects of their physico-chemical properties on CO2 capture ability. Three different amino-silane species were used: 3-aminopropyltriethoxysilane (APTS), 3-(2-aminoethyl)aminopropyltrimethoxysilane (EAPTS) and 3-[2-(2-aminoethyl)aminoethyl] aminopropyltrimethoxysilane (PAPTS). More specifically, samples were prepared by using two methods, following a post-synthesis grafting procedure and a one-pot preparation method. Experimental and computational techniques were used to study the structural and textural properties of the obtained samples and their surface species in relation to the adopted preparation method. For the most reactive samples, additional hints on the interactions of organosilane species with the silica surface were obtained by a combination of IR and SS-NMR spectroscopy, with particular emphasis on the effects of the silane chain length on the mobility of the organic species. Advanced complementary solid-state NMR techniques provided deeper information on the interactions of organosilane species with the silica surface. Finally, the amount of CO2 adsorbed was estimated by comparing the classical microcalorimetric analysis method with a new type of screening test, the Zero Length Column analysis, which is able to evaluate small amounts of samples in a very short time and the adsorption properties of the adsorbents. The reactivity of the amino-modified silica samples is deeply influenced by both the preparation route and by the type of organosilane used for the functionalization of the materials. In particular, samples prepared by the post-synthesis grafting procedure and containing higher amount of amino groups in the chain are more reactive, following the order PAPTS > EAPTS > APTS.

Experimental demonstration of a secondary source of partially polarized states.

We present a simple device that works as a secondary source of light with prescribed polarization properties. The device has great versatility, allowing complete control over both the degree of polarization and the Stokes vector that belongs to the fully polarized component of partially polarized light beams. We report experimental results that illustrate the device's versatility, by showing how polarized states can be moved within the Poincaré ball along spiraling paths.

Cu-based thin rolled foils: relationship among alloy composition, micromechanical and antiviral properties against SARS-CoV-2.

The healthcare-associated infections (HAIs) and pandemics caused by multidrug-resistant (MDR) and new-generation pathogens threaten the whole world community. Cu and its alloys have been attracting widespread interest as anti-contamination materials due to the rapid inactivation of MDR-superbugs and viruses. Applying thin Cu-based foils on pre-existing surfaces in hygiene-sensitive areas represents a quick, simple, cost-effective self-sanitising practice. However, the influence of chemical composition and microstructure should be deeply investigated when evaluating the antimicrobial capability and durability of Cu-based materials. The effect of composition on micromechanical and antiviral properties was investigated by comparing Cu15Zn and Cu18Ni20Zn (foil thickness from 13 to 27 µm) with Phosphorous High-Conductivity (PHC) Cu. The influence of recrystallisation annealing of PHC Cu was also investigated. Microstructural characterisation was carried out by optical (OM) and scanning electron (FEG-SEM) microscopy, Energy-dispersive Spectroscopy (EDS) and Electron-Backscattered Diffraction (EBSD). The micromechanical behaviour was assessed by microhardness, microscale abrasion and scratch tests. Cu-based foils were exposed to SARS-CoV-2 for different time points in quasi-dry conditions (artificial sweat solution), evaluating their antiviral capability by quantitative Reverse-Transcriptase Polymerase Chain Reaction (qRT-PCR). Surface morphology, contact angle measurements and Cu release were measured. All Cu-based surfaces completely inactivated SARS-CoV-2 in 10 min: pure Cu was the best option regarding antiviral efficiency, while Cu15Zn showed the best trade-off between micromechanical and antiviral properties.

New records of Trichinella patagoniensis from Argentina.

Trichinella spiralis was long considered the sole Trichinella species in Argentina. However, since 2004, various Trichinella species, including the encapsulated Trichinella patagoniensis and Trichinella britovi, as well as the unencapsulated Trichinella pseudospiralis, have been detected in the country. The present study aimed to identify Trichinella ML at the species level from cougars naturally infected from Argentina. To this end, muscle tissue samples from one cougar each from Córdoba, Neuquén, and Santa Cruz Provinces were individually analysed using the artificial digestion technique. DNA extraction and molecular identification of Trichinella species were conducted on individual muscle larvae by PCR amplification of the ESV region and subsequent PCR amplification and sequencing of the COI gene. Morphological analysis revealed muscle larvae with characteristics consistent with Trichinella genus. PCR revealed a single band of approximately 127 bp for each individual muscle larva. PCR amplification of the COI gene from each isolate generated a 309 bp band. Sequencing of the mitochondrial COI gene confirmed the identity of the parasite as T. patagoniensis. The present study documents new occurrences of T. patagoniensis in Puma concolor from Argentina, including the first detection of T. patagoniensis in Puma concolor from Córdoba and Neuquén Province. These findings expand the limited knowledge of T. patagoniensis distribution in Argentina.

Superradiant cascade in a seeded free-electron laser.

We report measurements demonstrating the concept of the free-electron laser (FEL) superradiant cascade. Radiation (λ(rad) = 200 nm) at the second harmonic of a short, intense seed laser pulse (λ(seed) = 400 nm) was generated by the cascaded FEL scheme at the transition between the modulator and radiator undulator sections. The superradiance of the ultrashort pulse is confirmed by detailed measurements of the resulting spectral structure, the intensity level of the produced harmonics, and the trend of the energy growth along the undulator. These results are compared to numerical particle simulations using the FEL code GENESIS 1.3 and show a satisfactory agreement.

Observation of time-domain modulation of free-electron-laser pulses by multipeaked electron-energy spectrum.

We present the experimental demonstration of a new scheme for the generation of ultrashort pulse trains based on free-electron-laser (FEL) emission from a multipeaked electron energy distribution. Two electron beamlets with energy difference larger than the FEL parameter ρ have been generated by illuminating the cathode with two ps-spaced laser pulses, followed by a rotation of the longitudinal phase space by velocity bunching in the linac. The resulting self-amplified spontaneous emission FEL radiation, measured through frequency-resolved optical gating diagnostics, reveals a double-peaked spectrum and a temporally modulated pulse structure.

The interactions of methyl tert-butyl ether on high silica zeolites: a combined experimental and computational study.

In this work, the interactions of methyl tert-butyl ether (MTBE) on different dealuminated high silica zeolites were studied by means of both experimental and computational approaches. Zeolites with different textural and surface features were selected as adsorbents and the effect of their physico-chemical properties (i.e. pore size architecture and type and amount of surface OH sites) on sorption capacity were studied. High silica mordenite (MOR) and Y zeolites (both with a SiO2/Al2O3 ratio of 200) and ZSM-5 solid (SiO2/Al2O3 ratio of 500) were selected as model sorbents. By combining FTIR and SS-NMR (both (1)H and (13)C CPMAS NMR) spectroscopy it was possible to follow accurately the MTBE adsorption process on highly defective MOR characterized by a high concentration of surface SiOH groups. The adsorption process is found to occur in different steps and to involve isolated silanol sites, weakly interacting silanols, and the siloxane network of the zeolite, respectively. H-bonding and van der Waals interactions occurring between the mordenite surface and MTBE molecules were modeled by DFT calculations using a large cluster of the MOR structure where two adjacent side-pockets were fused in a large micropore to simulate a dealumination process leading to silanol groups. This is the locus where MTBE molecules are more strongly bound and stabilized. FTIR spectroscopy and gravimetric measurements allowed determination of the interaction strength and sorption capacities of all three zeolites. In the case of both Y and MOR zeolites, medium-weak H-bonding with isolated silanols (both on internal and external zeolite surfaces) and van der Waals interactions are responsible for MTBE adsorption, whereas ZSM-5, in which a negligible amount of surface silanol species is present, displays a much lower amount of adsorbed MTBE retained mainly through van der Waals interactions with zeolite siloxane network.

High-order-harmonic generation and superradiance in a seeded free-electron laser.

Higher order harmonic generation in a free-electron laser amplifier operating in the superradiant regime [R. H. Dicke, Phys. Rev. 93, 99 (1954).] has been observed. Superradiance has been induced by seeding a single-pass amplifier with the second harmonic of a Ti:sapphire laser, generated in a ß-Barium borate crystal, at seed intensities comparable to the free-electron laser saturation intensity. Pulse energy and spectral distributions of the harmonics up to the 11th order have been measured and compared with simulations.