Orbital Excitations Research Articles

Interpretation of recently discovered single bottom baryons in the relativistic flux tube model

Following recent experimental progress in the study of bottom baryons, we systematically calculate the mass spectra of Λb, Ξb, Σb, Ξb′, and Ωb baryons with a quark-diquark picture in the framework of a relativistic flux tube model with spin-dependent interactions in the j-j coupling scheme. Furthermore, we calculate the strong decay width of bottom baryons decaying into a bottom baryon and a light pseudoscalar meson. Good agreement is found between the calculated masses and the experimentally available masses of singly bottom baryons. By analyzing both mass spectra and strong decay widths, we interpret Σb(6097) as a 1P(3/2−) state and Ξb(6100) as a 1P(1/2−) state of the Ξb baryon. The Ξb(6227) is identified to be an orbital excitation 1P of the Ξb′ baryon with JP=3/2−. Further, we determine Ξb(6327) and Ξb(6333) as a 1P(3/2−) state and 1P(5/2−) state, respectively, of Ξb′ baryon. From the obtained mass spectra, we construct the Regge trajectories in the (J,M2) plane, which are found to be essentially linear, parallel, and equidistant. Our predictions for higher orbital and radial excited states can help experimentalists identify missing excited states of singly bottom baryons. Published by the American Physical Society 2024

Cascade Ξ0 baryon spectroscopy in the relativistic framework of an independent quark model

The spectroscopy of Ξ0 is performed within the relativistic framework of independent quark model. The equal mixture of scalar and vector components in the potential having Martin-like form is considered for the confinement. With the suitable potential parameters for Ξ0, mass spectra for high radial and orbital excitation is calculated. The experimentally observed values of the ground-state magnetic moment, branching ratios, and asymmetry parameters for radiative weak decays, Ξ0→Λ0+γ0 and Ξ0→Σ0+γ0 are obtained to validate the model. The spin parity of experimentally known resonances like Ξ(1530), Ξ(1820), and Ξ(2030) are confirmed through the Regge trajectories in (J,M2) plane. The spin parity of Ξ(1950), Ξ(2130), and Ξ(2250) are predicted using those Regge trajectories. The radiative decay width and magnetic moment of first resonance is also predicted. Published by the American Physical Society 2024

Optical control of 4f orbital state in rare-earth metals.

A change of orbital state alters the coupling between ions and their surroundings drastically. Orbital excitations are hence key to understand and control interaction of ions. Rare-earth elements with strong magneto-crystalline anisotropy (MCA) are important ingredients for magnetic devices. Thus, control of their localized 4f magnetic moments and anisotropy is one major challenge in ultrafast spin physics. With time-resolved x-ray absorption and resonant inelastic scattering experiments, we show for Tb metal that 4f-electronic excitations out of the ground-state multiplet occur after optical pumping. These excitations are driven by inelastic 5d-4f-electron scattering, altering the 4f-orbital state and consequently the MCA with important implications for magnetization dynamics in 4f-metals and more general for the excitation of localized electronic states in correlated materials.

Predicted Ξb(6087)0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varXi _b(6087)^0$$\\end{document} and further predictions

The methods of QCD sum rules and light-cone sum rules within the framework of heavy quark effective theory have been widely applied to study the singly heavy baryons, and especially, we have applied these methods to predict not only the mass and width of the Ξb(6087)0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varXi _b(6087)^0$$\\end{document} recently discovered by LHCb, but also its observation channel and its mass difference from the Ξb(6100)-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varXi _b(6100)^-$$\\end{document}. We apply the same approach to perform a complete study on the P-wave bottom baryons of the SU(3) flavor 3¯F\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\bar{\ extbf{3}}}_F$$\\end{document} and investigate their fine structure. Besides the Λb(5912)0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varLambda _b(5912)^0$$\\end{document}, Λb(5920)0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varLambda _b(5920)^0$$\\end{document}, Ξb(6087)0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varXi _b(6087)^0$$\\end{document}, and Ξb(6100)-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varXi _b(6100)^-$$\\end{document}, our results suggest the existence of the other two Λb\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varLambda _b$$\\end{document} and two Ξb\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varXi _b$$\\end{document} baryons, whose widths are limited. They are the Λb(JP=3/2-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varLambda _b(J^P = 3/2^-)$$\\end{document} with the mass and width about (5.93-0.13+0.13GeV,0.0-0.0+12.0MeV)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(5.93^{+0.13}_{-0.13}~\ extrm{GeV},\\,0.0^{+12.0}_{-~0.0}~\ extrm{MeV})$$\\end{document}, the Λb(5/2-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varLambda _b(5/2^-)$$\\end{document} with (5.94-0.13+0.13GeV,≈0MeV)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(5.94^{+0.13}_{-0.13}~\ extrm{GeV},\\,\\approx 0~\ extrm{MeV})$$\\end{document}, the Ξb(3/2-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varXi _b(3/2^-)$$\\end{document} with (6.10-0.10+0.15GeV,1.4-1.4+11.6MeV)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(6.10^{+0.15}_{-0.10}~\ extrm{GeV},\\, 1.4{^{+11.6}_{-~1.4}}~\ extrm{MeV})$$\\end{document}, and the Ξb(5/2-)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varXi _b(5/2^-)$$\\end{document} with (6.11-0.10+0.15GeV,1.0-1.0+7.4MeV)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(6.11^{+0.15}_{-0.10}~\ extrm{GeV},\\,1.0{^{+7.4}_{-1.0}}~\ extrm{MeV})$$\\end{document}. Their mass splittings are calculated to be MΛb(5/2-)-MΛb(3/2-)=17±7MeV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_{\\varLambda _b(5/2^-)} - M_{\\varLambda _b(3/2^-)} = 17\\pm 7~\ extrm{MeV}$$\\end{document} and MΞb(5/2-)-MΞb(3/2-)=14±7MeV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_{\\varXi _b(5/2^-)} - M_{\\varXi _b(3/2^-)} = 14\\pm 7~\ extrm{MeV}$$\\end{document}. All these baryons are explained as the P-wave bottom baryons of the ρ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho $$\\end{document}-mode, where the orbital excitation is between the two light quarks. However, the existence of this mode is still controversial, so their experimental searches can verify both our approach and the existence of the ρ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho $$\\end{document}-mode, which can significantly improve our understanding on the internal structure of hadrons.

Collective Nature of Orbital Excitations in Layered Cuprates in the Absence of Apical Oxygens.

We have investigated the 3d orbital excitations in CaCuO_{2} (CCO), Nd_{2}CuO_{4} (NCO), and La_{2}CuO_{4} (LCO) using high-resolution resonant inelastic x-ray scattering. In LCO they behave as well-localized excitations, similarly to several other cuprates. On the contrary, in CCO and NCO the d_{xy} orbital clearly disperses, pointing to a collective character of this excitation (orbiton) in compounds without apical oxygen. We ascribe the origin of the dispersion as stemming from a substantial next-nearest-neighbor (NNN) orbital superexchange. Such an exchange leads to the liberation of the orbiton from its coupling to magnons, which is associated with the orbiton hopping between nearest neighbor copper sites. Finally, we show that the exceptionally large NNN orbital superexchange can be traced back to the absence of apical oxygens suppressing the charge transfer energy.

Heavy quark dominance in orbital excitation of singly and doubly heavy baryons

A mechanism of the heavy quark dominance in the orbital excitation is proposed in this paper which is testified to be reasonable for singly and doubly heavy baryons. In the relativistic quark model, an analysis of the Hamiltonian figures out the mechanism that the excitation mode with lower energy levels is always associated with the heavy quark(s), and the splitting of the energy levels is suppressed by the heavy quark(s). So, the heavy quarks dominate the orbital excitation of singly and doubly heavy baryons. Furthermore, a physical understanding of this mechanism is given in a semi-classical way. Accordingly, the predicted mass spectra of singly and doubly heavy baryons confirm the rationality of this mechanism. In addition, an interesting consequence of this mechanism is that a heavy-light meson is more likely to be produced in the strong decay of the high-orbital excited states, which is supported by experiments. This mechanism is rooted in the breakdown of the mass symmetry. Therefore, it may be also valid for other multi-quark systems, such as the tetraquarks Qqqq and QQqq, or the pentaquarks Qqqqq and QQqqq.

Mass spectra, Regge trajectories and decay properties of heavy-flavour mesons

In this article, we study the mass spectra, Regge trajectories and decay properties of heavy-flavour mesons $Q\bar{Q}$ $(Q=c,b)$ within a non-relativistic quark model. The spin hyperfine interaction is used to get the prediction for the heavy-meson masses for radial and orbital excitations. By using the radial and orbital excitations, we construct Regge trajectories for the heavy-mesons in the $(J,M^2)$ and $(n,M^2)$ plane and find their slopes and intercepts. We have computed leptonic, photonic and gluonic decay widths of heavy flavour mesons with and without QCD correction factor. We have compared our results of masses as well as decay widths with other theoretical and lattice QCD predictions for each states. Moreover, the known experimental results are also reasonably close to our predicted results.

Resonant inelastic X-ray scattering applications in quantum materials

The essence of quantum materials lies in the intricate coupling among charge, spin, orbital and lattice degrees of freedom. Although X-ray photoemission spectroscopy and inelastic neutron scattering have advantages in detecting fermionic single-particle spectral function and bosonic spin excitations in quantum materials, respectively, probing other bosonic collective excitations especially their coupling is not possible until the establishment of the advanced resonant inelastic X-ray scattering (RIXS). In the past decades, RIXS has flourished with continuously improved energy resolution which made a paradigm shift from measuring crystal-field splitting and the charge-transfer excitation, to probing collective excitations and the order parameters of all degrees of freedom. This review paper summarises the latest research progress of quantum materials studied by the soft X-ray RIXS. For instance, three-dimensional collective charge excitations, plasmons, were discovered experimentally by RIXS in both electron and hole doped cuprate superconductors. The collective orbital excitations and excitons were found in copper and nickel based quantum materials. For the newly discovered nickelate superconductors, RIXS has made substantial contributions to characterising their electronic and magnetic excitations and the related ordering phenomena critical for an in-depth understanding of the underlying superconducting mechanicsm. The RIXS is a unique tool in probing the higher-order spin excitations in quantum materials due to the strong spin-orbit coupling and the core-valence exchange interaction. The RIXS is also found to be superior in probing the Stoner magnetic excitations in magnetic metals and topological magnetic materials. Finally, the development of RIXS technology in Chinese large-scale research facilities is briefly prospected.

Preparation of chlorophyll compounds and simulation of DFT optical properties assisted screening of photosensitizers from Ginkgo biloba leaves

Chlorophyll compounds (Chls) from Ginkgo biloba leaves (GBL) are non-toxic natural pigments characterized by highly conjugated molecules and special spectra, making them ideally potential photosensitizers (PSs) in photodynamics therapy (PDT). In this study, 4 Chls were isolated from Ginkgo biloba polyprenols (GBPPs) wastes by using silica gel column separation and high performance liquid chromatography (HPLC). In addition, two new chlorophyll derivatives were successfully synthesized with chlorin e6 as the primary raw material. To evaluate and identify superior chlorophyll PSs, Density Functional Theory (DFT) and Density Functional Theory (TD-DFT)were employed to decode the microscopic and spectral properties of Ginkgo biloba Chls (GBChls). The spectral absorption, optical stability and reactive oxygen species (ROS) production of GBChls were further analyzed through comparisons of their frontier molecular orbital layout, charge distribution and excitation energy properties. Our results show that about 63 % absorption in the Q band for 14 GBChls comes from the π⇢π* transition from the highest occupied orbital (HOMO) to the lowest unoccupied orbital (LUMO), indicating the favorable delocalization effect of these GBChls. In particular, those GBChls with the long chain of the phytyl group exhibited higher total electron energy and thus could significantly increase the light stability. However, the large spatial volume and hydrophobicity of these compounds with the phytyl group chain was unfavorable for cellular uptake, leading to low ROS in cells. The electronegativity of porphin macrocycles in GBChls positively correlates with the intracellular ROS production rate, meaning that the former likely promotes the energy transfer between PSs and molecular oxygen during type II photoreaction. Among the GBChls, chlorin e6 demonstrated the highest ROS yields in DMF, while purpurin 18 compounds displayed long-wavelength absorption (698 nm), strong Q-band absorption, good optical stability, and high intracellular ROS production. Our findings highlight that chlorin e6 and purpurin 18 are most potential PSs anticancer drugs and offer new research perspectives for the processing and utilization of GBL resources.

Evidence for Low-level Dynamical Excitation in Near-resonant Exoplanet Systems* * This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.

The geometries of near-resonant planetary systems offer a relatively pristine window into the initial conditions of exoplanet systems. Given that near-resonant systems have likely experienced minimal dynamical disruptions, the spin–orbit orientations of these systems inform the typical outcomes of quiescent planet formation, as well as the primordial stellar obliquity distribution. However, few measurements have been made to constrain the spin–orbit orientations of near-resonant systems. We present a Rossiter–McLaughlin measurement of the near-resonant warm Jupiter TOI-2202 b, obtained using the Carnegie Planet Finder Spectrograph on the 6.5 m Magellan Clay Telescope. This is the eighth result from the Stellar Obliquities in Long-period Exoplanet Systems survey. We derive a sky-projected 2D spin–orbit angle and a 3D spin–orbit angle , finding that TOI-2202 b—the most massive near-resonant exoplanet with a 3D spin–orbit constraint to date—likely deviates from exact alignment with the host star’s equator. Incorporating the full census of spin–orbit measurements for near-resonant systems, we demonstrate that the current set of near-resonant systems with period ratios P 2/P 1 ≲ 4 is generally consistent with a quiescent formation pathway, with some room for low-level (≲20°) protoplanetary disk misalignments or post-disk-dispersal spin–orbit excitation. Our result constitutes the first population-wide analysis of spin–orbit geometries for near-resonant planetary systems.

Conformational stability, quantum computational (DFT), vibrational, electronic and non-covalent interactions (QTAIM, RDG and IGM) of antibacterial compound N-(1-naphthyl)ethylenediamine dihydrochloride

Naphthalene derivatives are heterocyclic compounds with significant applications in the pharmaceutical and biomedical industries. Several spectroscopy methods, including FT-IR, FT-Raman, and UV–Vis, were used in this study to examine the molecular structure of N-(1-Naphthyl) ethylenediamine dihydrochloride (NEDD). By employing DFT through the WB97XD with the level of 6–311++G(d, p) as the basis set, the optimized geometrical characteristics and full vibrational allocations of frequencies by the potential energy distribution were generated and matched to the experimental data. The delocalization of charge caused by intermolecular connections becomes apparent in the natural bond orbital (NBO) study. Additionally, frontier molecular orbital bandgap energy and electron excitation analyses were acquired to provide a deeper understanding of the structural characteristics of NEDD. Frontier molecular orbital energies revealed an energy band gap of 5.505 eV, demonstrating the existence of charge transfer within the molecule. Electronic transitions seen in the experimentally recorded UV–visible spectra were assigned using the TD-DFT method whereas transition density matrix (TDM) plots showed the ability to transmit charges. Considering wave function-derived parameters like the Laplacian of electron density (LED), local information entropy (LIE), the average localized ionization energy (ALIE) as well as non-covalent interactions, provides essential insights into the reactivity and stability traits of molecular systems. Local reactivity descriptions aided in understanding the interactions of physiologically relevant molecular systems, thereby facilitating the discovery of potential pharmaceutical compounds. Drug-likeness and ADMET assessment were achieved to assess biological properties of NEDD. Antibacterial assay confirmed its effectiveness against bacterial strains, while molecular docking studies. The stability of the best docked protein has been investigated using 70 ns molecular dynamics simulation followed by effective free energy calculation using MMPBSA.

Distinct spin and orbital dynamics in Sr2RuO4

The unconventional superconductor Sr2RuO4 has long served as a benchmark for theories of correlated-electron materials. The determination of the superconducting pairing mechanism requires detailed experimental information on collective bosonic excitations as potential mediators of Cooper pairing. We have used Ru L3-edge resonant inelastic x-ray scattering to obtain comprehensive maps of the electronic excitations of Sr2RuO4 over the entire Brillouin zone. We observe multiple branches of dispersive spin and orbital excitations associated with distinctly different energy scales. The spin and orbital dynamical response functions calculated within the dynamical mean-field theory are in excellent agreement with the experimental data. Our results highlight the Hund metal nature of Sr2RuO4 and provide key information for the understanding of its unconventional superconductivity.

Molecular electronic stopping cross section for H and He beams colliding with water: projectile charge state contribution

Abstract When an ion beam impinges on a target material, electron stripping and capture processes involve different charge fraction states in the beam, such that each projectile charge state produces a different energy-loss. In this work, the energy deposition of swift hydrogen and helium ion beams colliding with a water target in the gas phase is studied. The electronic structure of the molecular target is represented in terms of core, bond, and lone pair orbital decomposition within a Harmonic Oscillator representation. In this way, the stopping cross section becomes only a function of the orbital mean excitation energy, I 0i . The ion beam charge fraction compositions colliding on water is determined from the work of Wedlund et al (2019) Astronomy & Astrophysics, 630, A36) by accounting for the electron transfer cross sections. We find that the larger the projectile charge state, the larger the electronic stopping cross section and that the beam charge fraction determines the position of the maximum of the electronic stopping curve. Also, in agreement with the experiment, evidence is given on the dominant role of the largest projectile charge state in defining the stopping cross section for high energy collisions, while for low collision energies it is the lowest charge state together with all possible charge states contributing at the maximum of the electronic stopping cross section curve. Our results are reported and compared to available experimental data showing an excellent agreement to the available literature.

Complex Linear Response Functions for a Multiconfigurational Self-Consistent Field Wave Function in a High Performance Computing Environment.

We present novel developments for the highly efficient evaluation of complex linear response functions of a multiconfigurational self-consistent field (MCSCF) wave function as implemented in MultiPsi. Specifically, expressions for the direct evaluation of linear response properties at given frequencies using the complex polarization propagator (CPP) approach have been implemented, within both the Tamm-Dancoff approximation (TDA) and the random phase approximation (RPA). Purely real algebra with symmetric and antisymmetric trial vectors in a shared subspace is used wherein the linear response equations are solved. Two bottlenecks of large scale MC-CPP calculations, namely, the memory footprint and computational time, are addressed. The former is addressed by limiting the size of the subspace of trial vectors by using singular value decomposition (SVD) on either orbital or CI subspaces. The latter is addressed using an efficient parallel implementation as well as the strategy of dynamically adding linear response equations at near-convergence to neighboring roots. Furthermore, a novel methodology for decomposing MC-CPP spectra in terms of intuitive orbital excitations in an approximate fashion is presented. The performance of the code is illustrated with several numerical examples, including the X-ray spectrum of a molecule with nearly one hundred atoms. Additionally, for X-ray spectroscopy, the effect of including or excluding the core orbital in the active space on small covalent metal complexes is discussed.

Calculation of the one- and two-photon absorption spectra of water-soluble stilbene derivatives using a multiscale QM/MM approach.

We calculated the one- (OPA) and two-photon absorption (TPA) spectra of two large water-soluble stilbene derivatives presenting TPA cross sections of about 400 GM. However, the reported experimental TPA spectra present a spectral gap region, and a theoretical study of these promising molecules seems now timely and relevant. These molecules are composed of 200 or more atoms, becoming a challenge to obtain the TPA spectra even using density functional theory at the time-dependent quadratic response formalism. Thus, both OPA and TPA were also calculated using the INDO-S semi-empirical method. We used explicit solvent molecules using the sequential-quantum mechanics/molecular mechanics to include the solvent effects. Our results show that different transitions are participating in the OPA and TPA processes and that exchange-correlation functionals, including larger Hartree-Fock contributions, provide a better description of the OPA spectra; however, the opposite trend is observed on the TPA spectra. Alternatively, INDO-S/CISD, including contributions from single and double excitations, systematically describes both OPA and TPA bands with similar shifts and better reproduces the relative intensities of the two TPA bands compared to the experimental ones. The OPA spectra are characterized by a Highest Occupied Molecular Orbital-Lowest Unoccupied Molecular Orbital (HOMO-LUMO) excitation, while the low-energy TPA band is ascribed to a single transition encompassing the (HOMO-1)-LUMO and HOMO-(LUMO+1) excitations and the high-energy one is a combination of several transitions. Thus, although more studies are required to better assess the capability of the INDO-S/CISD method in describing the TPA spectra of large molecules, our results corroborate that it is a promising alternative.

Synergistic effect of Zn2GeO4 nanorod decorated metal organic framework ZIF-67 and its metal ligand charge transfer effect towards the photocatalytic CO2 reduction and C–C coupling

Metal-organic framework (MOF) especially zeolitic imidazole framework (ZIF-67) has shown tremendous efficiency in the field of CO2 adsorption, storage, and conversion due to its huge surface area and metal ligand charge transfer effect. A metal organic imidazole framework-based heterojunction, Zn2GeO4/ZIF-67 nanocomposite has been successfully synthesized where Zn2GeO4 nanorod deposited on the surface of high crystalline ZIF-67 to form an electronic Z scheme mechanism. The Zn2GeO4/ZIF-67 nanocomposite containing 20% Zn2GeO4 nanorod exhibit at about 1.62 times higher methanol production (41.16 μmol/g) than pure ZIF-67 (25.39 μmol/g) and the highest ethanol production was 1.53 times higher (32.66 μmol/g) than pure ZIF-67 (21.34 μmol/g) after 8 h of light irradiation. The electronic interaction of ZIF-67 and Zn2GeO4 has been studied theoretically using density functional theory calculation. Molecular orbital transition and excitation states were also calculated using time-dependent density functional theory calculation. The reaction pathway for CO2 reduction was determined by calculating free energy for each charge transfer intermediates.

Blueprint of a Scalable Spin Qubit Shuttle Device for Coherent Mid-Range Qubit Transfer in Disordered Si/SiGe/SiO2

Silicon spin qubits stand out due to their very long coherence times, compatibility with industrial fabrication, and prospect to integrate classical control electronics. To achieve a truly scalable architecture, a coherent mid-range link that moves the electrons between qubit registers has been suggested to solve the signal fan-out problem. Here, we present a blueprint of such a link of 10 μm length, called a spin qubit shuttle, which is based on connecting an array of gates into a small number of sets. To control these sets, only a few voltage control lines are needed and the number of these sets and thus the number of required control signals is independent of the length of this link. We discuss two different operation modes for the spin qubit shuttle: a qubit conveyor, i.e., a potential minimum that smoothly moves laterally, and a bucket brigade, in which the electron is transported through a series of tunnel-coupled quantum dots by adiabatic passage. We find the former approach more promising considering a realistic Si/SiGe device, including potential disorder from the charged defects at the Si/SiO2 layer, as well as typical charge noise. Focusing on the qubit transfer fidelity in the conveyor shuttling mode, we discuss in detail motional narrowing, the interplay between orbital and valley excitation and relaxation in the presence of g factors that depend on orbital and valley state of the electron, and effects from spin hotspots. We find that a transfer fidelity of 99.9% is feasible in Si/SiGe at a speed of approximately 10m/s, if the average valley splitting and its inhomogeneity stay within realistic bounds. Operation at low global magnetic field approximately equal to 20mT and material engineering towards high valley splitting is favorable for reaching high fidelities of transfer.12 MoreReceived 10 March 2022Revised 18 October 2022Accepted 15 February 2023DOI:https://doi.org/10.1103/PRXQuantum.4.020305Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum information with solid state qubitsQuantum transportSpin coherenceSpin relaxationSurface & interfacial phenomenaPhysical SystemsQuantum dotsSemiconductor compoundsCondensed Matter, Materials & Applied PhysicsQuantum Information

Population III star formation in an X-ray background: III. Periodic radiative feedback and luminosity induced by elliptical orbits

ABSTRACTWe model Pop III star formation in different FUV and X-ray backgrounds, including radiation feedback from protostars. We confirm previous results that a moderate X-ray background increases the number of Pop III systems per unit cosmological volume, but masses and multiplicities of the system are reduced. The stellar mass function also agrees with previous results, and we confirm the outward migration of the stars within the protostellar discs. We find that nearly all Pop III star systems are hierarchical, i.e. binaries of binaries. Typically, two equal-mass stars form near the centre of the protostellar disc and migrate outwards. Around these stars, mini-discs fragment forming binaries that also migrate outwards. Stars may also form at Lagrange points L4/L5 of the system. Afterwards, star formation becomes more stochastic due to the large multiplicity, and zero-metallicity low-mass stars can form when rapidly ejected from the disc. Stars in the disc often have eccentric orbits, leading to a periodic modulation of their accretion rates and luminosities. At the pericentre, due to strong accretion, the star can enter a red-supergiant phase reaching nearly Eddington luminosity in the optical bands (mAB ∼ 34 for a 100 M⊙ star at z = 6). During this phase, the star, rather than its nebular lines, can be observed directly by JWST, if sufficiently magnified by a gravitational lens. The ∼10 000 AU separations and high eccentricities of many Pop III star binaries in our simulations are favourable parameters for IMBH mergers – and gravitational waves emission – through orbital excitation by field stars.

Dynamics of photoinduced ferromagnetism in oxides with orbital degeneracy

By using intense coherent electromagnetic radiation, it may be possible to manipulate the properties of quantum materials very quickly, or even induce new and potentially useful phases that are absent in equilibrium. For instance, ultrafast control of magnetic dynamics is crucial for a number of proposed spintronic devices, and it can also shed light on the possible dynamics of correlated phases out of equilibrium. Inspired by recent experiments on spin-orbital ferromagnet ${\mathrm{YTiO}}_{3}$, we consider the nonequilibrium dynamics of a Heisenberg ferromagnetic insulator with low-lying orbital excitations. We model the dynamics of the magnon excitations in this system following an optical pulse that resonantly excites infrared-active phonon modes. As the phonons ring down, they can dynamically couple the orbitals with the low-lying magnons, leading to a dramatically modified effective bath for the magnons. We show that this transient coupling can lead to a dynamical acceleration of the magnetization dynamics, which is otherwise bottlenecked by small anisotropy. Exploring the parameter space more, we find that the magnon dynamics can also even completely reverse, leading to a negative relaxation rate when the pump is blue-detuned with respect to the orbital bath resonance. We therefore show that by using specially targeted optical pulses, one can exert a much greater degree of control over the magnetization dynamics, allowing one to optically steer magnetic order in this system. We conclude by discussing interesting parallels between the magnetization dynamics we find here and recent experiments on photoinduced superconductivity, where it is similarly observed that depending on the initial pump frequency, an apparent metastable superconducting phase emerges.

Evolution of orbital excitations from insulating to superconducting MgTi2O4 films

Spinel oxides are well-known functional materials but rarely show superconductivity. Recently, emergent superconductivity was discovered in ${\mathrm{MgTi}}_{2}{\mathrm{O}}_{4}$, which is attributed to the increase of electron doping and the suppression of orbital order. Here, we utilized Ti $L$-edge resonant inelastic x-ray scattering to study the orbital excitations in superconducting (SC) and insulating ${\mathrm{MgTi}}_{2}{\mathrm{O}}_{4}$ films. We find that the spectral weight of orbital excitations is enhanced and the energy of ${t}_{2g}$ intraband excitation is softened in the SC film compared to the insulating one, suggesting higher electron doping and a suppressed orbital order gap in the SC sample. These observations were further supported by our multiplet calculations using the minimal two-site model. Our results provide spectroscopic evidence for the competition between orbital order and superconductivity in ${\mathrm{MgTi}}_{2}{\mathrm{O}}_{4}$ and shed light on searching for novel superconductors in spinel oxides.