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Anatase TiO 2 is among the most studied materials for light-energy conversion applications, but the nature of its fundamental charge excitations is still unknown. Yet it is crucial to establish whether light absorption creates uncorrelated electron–hole pairs or bound excitons and, in the latter case, to determine their character. Here, by combining steady-state angle-resolved photoemission spectroscopy and spectroscopic ellipsometry with state-of-the-art ab initio calculations, we demonstrate that the direct optical gap of single crystals is dominated by a strongly bound exciton rising over the continuum of indirect interband transitions. This exciton possesses an intermediate character between the Wannier–Mott and Frenkel regimes and displays a peculiar two-dimensional wavefunction in the three-dimensional lattice. The nature of the higher-energy excitations is also identified. The universal validity of our results is confirmed up to room temperature by observing the same elementary excitations in defect-rich samples (doped single crystals and nanoparticles) via ultrafast two-dimensional deep-ultraviolet spectroscopy. Here the authors combine steady-state angle-resolved photoemission spectroscopy, ellipsometry and ultrafast two-dimensional ultraviolet spectroscopy to examine the role of many-body correlations in anatase TiO 2 , revealing the existence of strongly bound excitons in single crystals and nanoparticles.

A paradigmatic case of multi-band Mott physics including spin-orbit and Hund’s coupling is realized in Ca 2 RuO 4 . Progress in understanding the nature of this Mott insulating phase has been impeded by the lack of knowledge about the low-energy electronic structure. Here we provide—using angle-resolved photoemission electron spectroscopy—the band structure of the paramagnetic insulating phase of Ca 2 RuO 4 and show how it features several distinct energy scales. Comparison to a simple analysis of atomic multiplets provides a quantitative estimate of the Hund’s coupling J =0.4 eV. Furthermore, the experimental spectra are in good agreement with electronic structure calculations performed with Dynamical Mean-Field Theory. The crystal field stabilization of the d xy orbital due to c -axis contraction is shown to be essential to explain the insulating phase. These results underscore the importance of multi-band physics, Coulomb interaction and Hund’s coupling that together generate the Mott insulating state of Ca 2 RuO 4 . Detailed knowledge of the low-energy electronic structure is required to understand the Mott insulating phase of Ca 2 RuO 4 . Here, Sutter et al . provide directly the experimental band structure of the paramagnetic insulating phase of Ca 2 RuO 4 and unveil the electronic origin of its Mott phase.

A paradigmatic case of multi-band Mott physics including spin-orbit and Hund's coupling is realized in Ca RuO . Progress in understanding the nature of this Mott insulating phase has been impeded by the lack of knowledge about the low-energy electronic structure. Here we provide-using angle-resolved photoemission electron spectroscopy-the band structure of the paramagnetic insulating phase of Ca RuO and show how it features several distinct energy scales. Comparison to a simple analysis of atomic multiplets provides a quantitative estimate of the Hund's coupling J=0.4 eV. Furthermore, the experimental spectra are in good agreement with electronic structure calculations performed with Dynamical Mean-Field Theory. The crystal field stabilization of the d orbital due to c-axis contraction is shown to be essential to explain the insulating phase. These results underscore the importance of multi-band physics, Coulomb interaction and Hund's coupling that together generate the Mott insulating state of Ca RuO .

Overwhelming evidence indicates that cancer is a genetic disease caused by the accumulation of mutations in oncogenes and tumor suppressor genes. It is also increasingly apparent, however, that cancer depends not only on mutations in these coding genes but also on alterations in the large class of non-coding RNAs. Here, we report that one such long non-coding RNA, TRPM2-AS, an antisense transcript of TRPM2, which encodes an oxidative stress-activated ion channel, is overexpressed in prostate cancer (PCa). The high expression of TRPM2-AS and its related gene signature were found to be linked to poor clinical outcome, with the related gene signature working also independently of the patient's Gleason score. Mechanistically, TRPM2-AS knockdown led to PCa cell apoptosis, with a transcriptional profile that indicated an unbearable increase in cellular stress in the dying cells, which was coupled to cell cycle arrest, an increase in intracellular hydrogen peroxide and activation of the sense TRPM2 gene. Moreover, targets of existing drugs and treatments were found to be consistently associated with high TRPM2-AS levels in both targeted cells and patients, ultimately suggesting that the measurement of the expression levels of TRPM2-AS allows not only for the early identification of aggressive PCa tumors, but also identifies a subset of at-risk patients who would benefit from currently available, but mostly differently purposed, therapeutic agents.

The high- T c cuprate superconductors are close to antiferromagnetic order. Recent measurements of magnetic excitations have reported an intriguing similarity to the spin waves—magnons—of the antiferromagnetic insulating parent compounds, suggesting that magnons may survive in damped, broadened form throughout the phase diagram. Here we show by resonant inelastic X-ray scattering on Bi 2 Sr 2 CaCu 2 O 8+ δ (Bi-2212) that the analogy with spin waves is only partial. The magnon-like features collapse along the nodal direction in momentum space and exhibit a photon energy dependence markedly different from the Mott-insulating case. These observations can be naturally described by the continuum of charge and spin excitations of correlated electrons. The persistence of damped magnons could favour scenarios for superconductivity built from quasiparticles coupled to spin fluctuations. However, excitation spectra composed of particle–hole excitations suggest that superconductivity emerges from a coherent treatment of electronic spin and charge in the form of quasiparticles with very strong magnetic correlations. The nature of the relationship between the spin-ordered and superconducting states of the cuprates is a longstanding puzzle. X-ray measurements conducted by Guarise et al . suggest that a continuum model rather than overdamped magnon model provides a more complete picture of the spin spectrum of Bi 2 Sr 2 CaCu 2 O 8+ δ .

Unsteady simulations of the flow around two cylinders arranged in tandem are carried out using Scale-Adaptive Simulation (SAS) turbulence model for high subcritical Reynolds number (Re=2×〖10〗^5). Three-dimensional simulations are performed for different center-to-center distances between the cylinders (L/D varies 1.1 to 7, where D is cylinder diameter). The effects of the gaps between the cylinders are analyzed through the values of mean and fluctuating force coefficients, Strouhal number, pressure distribution, as well as through the wake flow structures behind both cylinders. The results are compared with published experimental data by different authors. The obtained results reveal good general agreement with the experimental data. Besides, to explore the effects of the interference, two tandem cylinders test are compared with a single cylinder case. The results show that this simple configuration (tandem) can strongly influence the flow pattern and forces on the cylinders. A critical nondimensional distance is obtained at L/D=3 at which two different flow patterns are identified, one pattern momentarily similar to the reattachment regime and another pattern similar to the co-shedding regime.

We report angle-resolved photoemission (ARPES) measurements, density functional and model tight-binding calculations on Ba2IrO4 (Ba-214), an antiferromagnetic (TN = 230 K) insulator. Ba-214 does not exhibit the rotational distortion of the IrO6 octahedra that is present in its sister compound Sr2IrO4 (Sr-214), and is therefore an attractive reference material to study the electronic structure of layered iridates. We find that the band structures of Ba-214 and Sr-214 are qualitatively similar, hinting at the predominant role of the spin-orbit interaction in these materials. Temperature-dependent ARPES data show that the energy gap persists well above TN, and favor a Mott over a Slater scenario for this compound.

Numerical investigations using Scale-Adaptive Simulation (SAS) turbulence model are carried out to study the flow around a circular cylinder near to a plane boundary at Reynolds numbers between 8.6x104 and 2.77x105 with two different boundary layer thickness (δ) on the plane. The effects of gap (G) between the cylinder and the plane, the Reynolds number and the thickness of the plane boundary layer are analyzed through the drag and the lift coefficients, the Strouhal number, as well as through the wake flow structures behind the cylinder. Two and three-dimensional simulations are performed to examine the significance of the flow three-dimensionality when the cylinder is located near a plane. The SAS model results are compared with published experimental data and numerical results for similar flow conditions. The characteristics of the wake structures and force acting on the cylinder are in good agreement with previous studies. In general, the 3D-SAS model performed better than 2D-SAS. Based on the numerical results here obtained, the SAS turbulence model can be applied to study this flow configuration.

In non-magnetic materials the combination of inversion symmetry breaking (ISB) and spin-orbit coupling (SOC) determines the spin polarization of the band structure. However, a local spin polarization can also arise in centrosymmetric crystals containing ISB subunits. This is namely the case for the nodal-line semimetal ZrSiTe where, by combining spin- and angle-resolved photoelectron spectroscopy with ab initio band structure calculations, we reveal a complex spin polarization. In the bulk, the valence and conduction bands exhibit opposite spin orientations in two spatially separated two-dimensional ZrTe sectors within the unit cell, yielding no net polarization. We also observe spin-polarized surface states that are well separated in energy and momentum from the bulk bands. A layer-by-layer analysis of the spin polarization allows us to unveil the complex evolution of the signal in the bulk states near the surface, thus bringing the intertwined nature of surface and bulk effects to the fore. Local inversion symmetry breaking in centrosymmetric materials can lead to large spin polarization of the electronic band structure in separate sectors of the unit cell. Here, the authors reveal such hidden spin polarisation in ZrSiTe using spin and angle resolved photoemission spectroscopy in combination with ab initio band structure calculations and investigate the resultant spin polarised bulk and surface properties

Mo 8 O 23 is a low-dimensional chemically robust transition metal oxide coming from a prospective family of functional materials, MoO 3− x , ranging from a wide gap insulator ( x  = 0) to a metal ( x  = 1). The large number of stoichometric compounds with intermediate x have widely different properties. In Mo 8 O 23 , an unusual charge density wave transition has been suggested to occur above room temperature, but its low temperature behaviour is particularly enigmatic. We present a comprehensive experimental study of the electronic structure associated with various ordering phenomena in this compound, complemented by theory. Density-functional theory (DFT) calculations reveal a cross-over from a semi-metal with vanishing band overlap to narrow-gap semiconductor behaviour with decreasing temperature. A buried Dirac crossing at the zone boundary is confirmed by angle-resolved photoemission spectroscopy (ARPES). Tunnelling spectroscopy (STS) reveals a gradual gap opening corresponding to a metal-to-insulator transition at 343 K in resistivity, consistent with CDW formation and DFT results, but with large non-thermal smearing of the spectra implying strong carrier scattering. At low temperatures, the CDW picture is negated by the observation of a metallic Hall contribution, a non-trivial gap structure in STS below ∼170 K and ARPES spectra, that together represent evidence for the onset of the correlated state at 70 K and the rapid increase of gap size below ∼30 K. The intricate interplay between electronic correlations and the presence of multiple narrow bands near the Fermi level set the stage for metastability and suggest suitability for memristor applications.