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Fluid catalytic cracking (FCC) slurry is a by-product of petrochemical industry rich in aromatics. In this paper, the effect of FCC slurry on the physical properties of SBS modified bitumen was investigated by softening point, penetration, ductility and low temperature flexibility test. The influence of FCC slurry on the compatibility of SBS modified bitumen was evaluated by fluorescence microscope and segregation test. The results show that FCC slurry improves the softening point, penetration, ductility and low temperature flexibility of SBS modified bitumen. Fluorescence microscope showed that FCC slurry promotes the dispersion of SBS in bitumen, which is conducive to the formation of network crosslinking structure of SBS modified bitumen. The segregation test indicated that the compatibility of SBS with bitumen was improved with the content of FCC slurry increasing.

We employ the fluctuation-exchange approximation to study the relation of superconducting pairing symmetries and density-wave fluctuations based on the extended triangular Hubbard model upon electron doping and interactions, with an possible application to the layered metal dichalcogenide SnSe2. For the case where the interactions between electrons contain only the on-site Hubbard term, the superconducting pairings are mainly mediated by spin fluctuations, and the spin-singlet pairing with the d-wave symmetry robustly dominates in the low and moderate doping levels, and a d-wave to extended s-wave transition is observed as the electron doping reaches n = 1. When the near-neighbor site Coulomb interactions are also included, the charge fluctuations are enhanced, and the spin-triplet pairings with the p-wave and f-wave symmetries can be realized in the high and low doping levels, respectively.

As a special order of electronic correlation induced by spatial modulation, the charge density wave (CDW) phenomena in condensed matters attract enormous research interests. Here, using scanning-tunneling microscopy in various temperatures, we observe a new (2×1) CDW phase besides the (√7×√3) CDW phase in epitaxial monolayer 1T-VSe2 film. Combining the variable-temperature angle-resolved photoemission spectroscopic (ARPES) measurements, we discover an anisotropic CDW gap and a two-step transition associated with the different CDW phases, which were observed below 135 K for the (√7×√3) CDW phase and between 135 K to 330 K for the (2×1) CDW phase respectively. The (√7×√3) CDW phase results a full gap, while the (2×1) CDW phase shows highly momentum dependence and results a partial gap structure at the Fermi surface. This two-step transition with anisotropic gap opening and the resulted evolution in ARPES spectra are corroborated by our theoretical calculation based on a phenomenological form for the self-energy containing a two-gap structure. Our findings provide significant information and deep understanding on the CDW phases in monolayer 1T-VSe2 film as a 2D material.

We introduce an entanglement entropy analysis to quantitatively identify the confinement and deconfinement of the spinons in the spin excitations of quantum magnets. Our proposal is implemented by the parton construction of a honeycomb-lattice antiferromagnet exhibiting high-energy anomalous spectra. To obtain the quasiparticles of spin excitations for entanglement entropy calculations, we develop an effective Hamiltonian using the random phase approximation. We elaborate quantitatively the deconfinement-to-confinement transition of spinons in the anomalous spectra with the increase of the Hubbard interaction, indicating the avoided fractionalization of magnons in the strong interaction regime. Meanwhile, the Higgs mode at the {\Gamma}0 point is fractionalized into four degenerate spinon pairs, although it appears as a sharp well-defined peak in the spectra. Our work extends our understanding of the deconfinement of the spinon and its coexistence with the magnon in quantum magnets., Comment: 6 pages, 4 figures

The elementary excitations from the conventional magnetic ordered states, such as ferromagnets and antiferromagnets, are magnons. Here, we elaborate a case where the well-defined magnons are absent completely and the spin excitation spectra exhibit an entire continuum in the itinerant edge ferromagnetic state of graphene arising from the flatband edge electronic states. Based on the further studies of the entanglement entropy and finite-size analysis, we show that the continuum other than the Stoner part results from the spin-1/2 spinons deconfined from magnons. The spinon continuum in a magnetically ordered state is ascribed to a ferromagnetic Luttinger liquid in this edge ferromagnet. The investigation is carried out by using the numerical exact diagonalization method with a projection of the interacting Hamiltonian onto the flat band., 7 pages, 7 figures

Dirac matters provide a platform for exploring the interplay of their carriers with other quantum phenomena. ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{1\ensuremath{-}y}{\mathrm{Sb}}_{2}$ has been proposed to be a magnetic Weyl semimetal and provides an excellent platform to study the coupling between Weyl fermions and magnons. Here, we report comprehensive inelastic neutron scattering (INS) measurements on single crystals of ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{1\ensuremath{-}y}{\mathrm{Sb}}_{2}$, which have been well characterized by magnetization and magnetotransport measurements, both of which demonstrate that the material is a topologically nontrivial semimetal. The INS spectra clearly show a spin gap of $\ensuremath{\sim}6$ meV. The dispersion in the magnetic Mn layer extends up to about 76 meV, while that between the layers has a narrow band width of 6 meV. We find that the linear spin-wave theory using a Heisenberg spin Hamiltonian can reproduce the experimental spectra with the following parameters: a nearest-neighbor ($S{J}_{1}\ensuremath{\sim}28.0$ meV) and next-nearest-neighbor in-plane exchange interaction ($S{J}_{2}\ensuremath{\sim}9.3$ meV), interlayer exchange coupling ($S{J}_{c}\ensuremath{\sim}\ensuremath{-}0.1$ meV), and spin anisotropy constant ($SD\ensuremath{\sim}\ensuremath{-}0.07$ meV). Despite the coexistence of Weyl fermions and magnons, we find no clear evidence that the magnetic dynamics are influenced by the Weyl fermions in ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{1\ensuremath{-}y}{\mathrm{Sb}}_{2}$, possibly because that the Weyl fermions and magnons reside in the Sb and Mn layers separately, and the interlayer coupling is weak due to the quasi-two-dimensional nature of the material, as also evident from the small $S{J}_{c}$ of $\ensuremath{-}0.1$ meV.

Kitaev quantum spin liquids described by the Kitaev model represent an exotic state of matter with long-range entangled spins and topological order, which hold promise for quantum computation. $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$, a material with van der Waals layered structure, is shown to be proximate to such a state recently. Here we report Raman spectroscopy of atomically thin $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$. New phonon modes emerge at low temperature, signifying a phase transition to a crystal structure with lowered symmetry. The Fano line shape of two low-energy phonon modes and the magnetic scattering continuum in bulk $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$, which evidence fractionalized Majorana fermions of the proximate quantum spin liquid, persist to the trilayer. Polarization-dependent measurements reveal increased anisotropy of the Kitaev exchange constants when approaching the two-dimensional limit. Our results demonstrate an intimate relation between the crystal structure and the symmetry of the proximate quantum spin liquid ground state.

We show that a suitable combination of flat-band ferromagnetism, geometry and nontrivial electronic band topology can give rise to itinerant topological magnons. An SU(2) symmetric topological Hubbard model with nearly flat electronic bands, on a Kagome lattice, is considered as the prototype. This model exhibits ferromagnetic order when the lowest electronic band is half-filled. Using the numerical exact diagonalization method with a projection onto this nearly flat band, we can obtain the magnonic spectra. In the flat-band limit, the spectra exhibit distinct dispersions with Dirac points, similar to those of free electrons with isotropic hoppings, or a local spin magnet with pure ferromagnetic Heisenberg exchanges on the same geometry. Significantly, the non-flatness of the electronic band may induce a topological gap at the Dirac points, leading to a magnonic band with a nonzero Chern number. More intriguingly, this magnonic Chern number changes its sign when the topological index of the electronic band is reversed, suggesting that the nontrivial topology of the magnonic band is related to its underlying electronic band. Our work suggests interesting directions for the further exploration of, and searches for, itinerant topological magnons.

Metallization of 1T-TaS_{2} is generally initiated at the domain boundary of a charge density wave (CDW), at the expense of its long-range order. However, we demonstrate in this study that the metallization of 1T-TaS_{2} can be also realized without breaking the long-range CDW order upon surface alkali doping. By using scanning tunneling microscopy, we find the long-range CDW order is always persisting, and the metallization is instead associated with additional in-gap excitations. Interestingly, the in-gap excitation is near the top of the lower Hubbard band, in contrast to a conventional electron-doped Mott insulator where it is beneath the upper Hubbard band. In combination with the numerical calculations, we suggest that the appearance of the in-gap excitations near the lower Hubbard band is mainly due to the effectively reduced on-site Coulomb energy by the adsorbed alkali ions.

In condensed matter physics, there is a novel phase termed "quantum spin liquid", in which strong quantum fluctuations prevent the long-range magnetic order from being established, and so the electron spins do not form an ordered pattern but remain "liquid" like even at absolute zero temperature. Such a phase is not involved with any spontaneous symmetry breaking and local order parameter, and to understand it is beyond the conventional phase transition theory. Due to the rich physics and exotic properties of quantum spin liquids, such as the long-range entanglement and fractional quantum excitations, which are believed to hold great potentials in quantum communication and computation, they have been intensively studied since the concept was proposed in 1973 by P. W. Anderson. Currently, experimental identifications of a quantum spin liquid still remain as a great challenge. Here, we highlight some interesting experimental progress that has been made recently. We also discuss some outstanding issues and raise questions that we consider to be important for future research., Comment: A short review paper published in npj Quantum Materials. Due to the limitation on the number of references, we are very unfortunate to miss many excellent ones

The Al-doped Mg2Si thin films were fabricated by two-target alternative magnetron sputtering technique, and the influences of different Al doping contents on the thermoelectric properties of Al-doped Mg2Si thin films were investigated. The compositions, crystal structures, electronic transport properties and thermoelectric properties of the thin films were examined using energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Hall coefficient measurement and Seebeck coefficient measurement system, respectively. The EDS results show that the thin films doped with Al target sputtering power of 30 W, 60 W and 90 W have the Al content of 0.68 at.%, 1.56 at.% and 2.85 at.%, respectively. XRD results indicate that the diffraction peaks of Mg2Si become stronger with increasing Al dopant. The results of Hall coefficient measurement and Seebeck coefficient measurement system reveal that all the samples are n-type. The conductivities of Al-doped Mg2Si thin films are significantly greater than that of undoped Mg2Si thin film, and increase with increasing Al doping content. With the increase of temperature, the absolute value of the Seebeck coefficients of Mg2Si base thin films increase firstly and then decrease. The maximum power factor obtained is 3.8 mW m−1 k−2 for 1.56 at.% Al-doped Mg2Si thin film at 573 K.

The confinement and deconfinement of spinons in the square-lattice antiferromagnetic ${J}_{1}\ensuremath{-}{J}_{2}$ Heisenberg model are elaborated by exploring the evolution of the whole excitation spectra with ${J}_{2}$, based on the spin cluster perturbation theory. We find that deconfined spin-$1/2$ spinons beyond the conventional spin-1 magnons have already emerged partially even in the limit ${J}_{2}=0$ and develop with ${J}_{2}$, exhibiting as a continuum close to $(\ensuremath{\pi},0)$ in the Brillouin zone. In the region near ${J}_{2}=0.5{J}_{1}$, the entire spectrum is characterized by a broad continuum in which all magnons are deconfined into spinons, whose ground state is attributed to a ${Z}_{2}$ quantum spin liquid with the aid of a variational-Monte-Carlo analysis. The spinon continua are also found in the stripe phase with ${J}_{2}g0.6{J}_{1}$. Our study provides spectroscopic evidences for the fractionalized excitations and quantum spin liquid and highlights the rising field to explore the exotic quantum phases from a perspective of excitation spectrum.

The magnetic properties of 4d and 5d transition-metal insulating compounds with the honeycomb structure are believed to be described by the Heisenberg-Kitaev model, which contains both the isotropic Heisenberg interaction J and anisotropic Kitaev interaction K. In this paper, to investigate the charge dynamics in these materials, we study the single-hole propagation of the t-J-K model in various magnetically ordered phases by the self-consistent Born approximation. We find that there are low-energy coherent quasiparticle (QP) excitations in all of these phases which appear firstly around the K point in the Brillouin zone (BZ), but the band-widths of these QPs are very small due to the hole-magnon coupling. Interestingly, in the zigzag phase relevant to recent experiments, though the QP weights are largely suppressed in the physical spectra in the first BZ, we find that they recover in the extended BZs. Moreover, our results reveal that the low-energy QP spectra are reduced with the increase of K., 9 pages, 5 figures

We study the Kitaev spin liquid (KSL) in a [001] magnetic field employing the mean field theory (MFT/MF) in the Majorana fermion representation. The MF Hamiltonian of the system has the Bogoliubov de-Gennes (BdG) form of a 2D Weyl superconductor. We discover a robust gapless regime in intermediate magnetic field for both gapless and gapped AFM KSL with Jx = Jy before the system is polarized in high magnetic field. A topological phase transition (PT) connecting two gapless phases with nodal lines takes place at a critical magnetic field hc1 in this regime. While the nodal lines at hc1 is protected by the mirror symmetry with Jx = Jy and disappear at Jx 6= Jy with a gap opening near the critical field, the nodal points at E = 0 can exist at intermediate fields even without mirror symmetry. We reveal that the phase evolution of the KSL in the magnetic field is driven by the competition between the magnetic field and the particle-hole (p-h) asymmetry of the normal state of the BdG Hamiltonian, which results in the robust intermediate gapless phase for AFM KSL. For FM KSL, there is no intermediate PT before polarization. The above phase diagrams are confirmed by dynamical MFT (DMFT) results., published version

By combining polarized pump-probe spectroscopic and Laue x-ray diffraction measurements, we have observed nonequivalent transient optical responses with the probe beam polarized along the $x$ and $y$ axes in overdoped $\mathrm{NaF}{\mathrm{e}}_{1\text{--}x}\mathrm{C}{\mathrm{o}}_{x}\mathrm{As}$ superconductors. Such transient anisotropic behavior has been uncovered in the tetragonal phase with the doping level and temperature range far from the borders of static nematic phases. The measured transient anisotropy can be well explained as a result of nematic fluctuation driven by an orbital order with energy splitting of the ${d}_{xz}$- and ${d}_{yz}$-dominant bands. In addition, the doping level dependence and the pressure effect of the crossover temperature show significant differences between the transient nematic fluctuation and static nematic phase, implying spin and orbital orders may play different roles in static and transient nematic behaviors.

We study the response of the Kitaev spin liquid (KSL) to a local magnetic field perpendicular to the Kitaev honeycomb lattice. The local magnetic field induces a dynamical excitation of a flux pair in the spin liquid and the system can be described by a generally particle-hole asymmetric interacting resonant level model. The dynamical excitation of the flux pair closes the flux gap in the spectrum of the spin correlation function locally for the gapless KSL even from the perturbative response to a weak magnetic field. Beyond the perturbative regime, the p-h asymmetry competes with the magnetic field and results in a rich phase diagram. Moreover, the magnetic field breaks the gauge equivalence of the ferromagnetic and anti-ferromagnetic Kitaev couplings of the ground state and leads to very different behaviors for the two cases. The anti-ferromagnetic case experiences a first order phase transition to the polarized state during magnetization whereas the ferromagnetic case does not. This study can be generalized to the Kitaev model in a uniform magnetic field and may help understand issues in recent experiments on KSL candidates., Comment: Published version

We study the spin-1 excitation spectra of the flatband ferromagnetic phases in interacting topological insulators. As a paradigm, we consider a quarter filled square lattice Hubbard model whose free part is the $\pi$ flux state with topologically nontrivial and nearly-flat electron bands, which can realize either the Chern or $Z_2$ Hubbard model. By using the numerical exact diagonalization method with a projection onto the nearly-flat band, we obtain the ferromagnetic spin-1 excitation spectra for both the Chern and $Z_2$ Hubbard models, consisting of spin waves and Stoner continuum. The spectra exhibit quite distinct dispersions for both cases, in particular the spin wave is gapless for the Chern Hubbard model, while gapped for the $Z_2$ Hubbard model. Remarkably, in both cases, the nonflatness of the free electron bands introduces dips in the lower boundary of the Stoner continuum. It significantly renormalizes the energies of the spin waves around these dips downward and leads to roton-like spin excitations. We elaborate that it is the softening of the roton-like modes that destabilizes the ferromagnetic phase, and determine the parameter region where the ferromagnetic phase is stable., Comment: Accepted by PRB

We report on comprehensive results identifying the ground state of a triangular-lattice structured YbZnGaO$_4$ to be spin glass, including no long-range magnetic order, prominent broad excitation continua, and absence of magnetic thermal conductivity. More crucially, from the ultralow-temperature a.c. susceptibility measurements, we unambiguously observe frequency-dependent peaks around 0.1 K, indicating the spin-glass ground state. We suggest this conclusion to hold also for its sister compound YbMgGaO$_4$, which is confirmed by the observation of spin freezing at low temperatures. We consider disorder and frustration to be the main driving force for the spin-glass phase., Version as accepted to PRL

Kitaev interactions underlying a quantum spin liquid have long been sought, but experimental data from which their strengths can be determined directly, are still lacking. Here, by carrying out inelastic neutron scattering measurements on high-quality single crystals of $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$, we observe spin-wave spectra with a gap of $\ensuremath{\sim}2\text{ }\text{ }\mathrm{meV}$ around the $M$ point of the two-dimensional Brillouin zone. We derive an effective-spin model in the strong-coupling limit based on energy bands obtained from first-principles calculations, and find that the anisotropic Kitaev interaction $K$ term and the isotropic antiferromagnetic off-diagonal exchange interaction $\mathrm{\ensuremath{\Gamma}}$ term are significantly larger than the Heisenberg exchange coupling $J$ term. Our experimental data can be well fit using an effective-spin model with $K=\ensuremath{-}6.8\text{ }\text{ }\mathrm{meV}$ and $\mathrm{\ensuremath{\Gamma}}=9.5\text{ }\text{ }\mathrm{meV}$. These results demonstrate explicitly that Kitaev physics is realized in real materials.

The spin fluctuations and superconducting pairing symmetries in the dispersive band of Lieb lattice are studied by fluctuation exchange approximation. The antiferromagnetic spin density wave is found to exist on the A sublattice (the lattice sites with four nearest neighbors) at half filling. When slightly doped away from half filling, a balance between the combined effects of the ( π , π ) and ( 0.4 π , 0 ) spin fluctuations and the gaining of the condensation energy leads to the nearly degenerate d x 2 − y 2 - and g x y ( x 2 − y 2 ) -wave pairing states. After further doped, the d x y -wave state is favored via the intra-sublattice spin fluctuations with a wave vector ( π , 0 ). We emphasize that the sublattices' contribution and the renormalization of the spectral function play a crucial role on the spin fluctuations and the pairing symmetry. The effect of the imbalance of the on-site energy at different sublattices is also discussed.

The local magnetism induced by vacancies in the presence of the spin-orbital interaction is investigated based on the half-filled Kane-Mele-Hubbard model on the honeycomb lattice. Using the self-consistent mean-field theory, we find that the spin-orbital coupling will enhance the localization of the spin moments near a single vacancy. We further study the magnetic structures along the zigzag edges formed by a chain of vacancies. We find that the spin-orbital coupling tends to suppress the counter-polarized ferrimagnetic order on the upper and lower edges, because of the open of the spin-orbital gap. As a result, in the case of the balance number of sublattices, it will suppress completely this kind of ferrimagnetic order. But, for the imbalance case, a ferrimagnetic order along both edges exists because additional zero modes will not be affected by the spin-orbital coupling., 6 pages, 6 figures

We study various particle–hole excitations and possible superconducting pairings mediated by these fluctuations in doped α-RuCl3 by using multi-band Hubbard model with all t2g orbitals. By performing a random-phase-approximation (RPA) analysis, we find that among all particle–hole excitations, the j eff = 1/2 pseudospin fluctuations are dominant, suggesting the robustness of j eff = 1/2 picture even in the doped systems. We also find that the most favorable superconducting state has a d-wave pairing symmetry.

We study the half-filled Hubbard model on the triangular lattice with spin-dependent Kitaev-like hopping. Using the variational cluster approach, we identify five phases: a metallic phase, a non-coplanar chiral magnetic order, a $120^\circ$ magnetic order, a nonmagnetic insulator (NMI), and an interacting Chern insulator (CI) with a nonzero Chern number. The transition from CI to NMI is characterized by the change of the charge gap from an indirect band gap to a direct Mott gap. Based on the slave-rotor mean-field theory, the NMI phase is further suggested to be a gapless Mott insulator with a spinon Fermi surface or a fractionalized CI with nontrivial spinon topology, depending on the strength of Kitaev-like hopping. Our work highlights the rising field that interesting phases emerge from the interplay of band topology and Mott physics., published version, references updated

In this paper, we investigate the quasiparticle scattering interference(QPI) in the nematic phase of iron pnictides, based on the magnetic and orbital scenarios of nematicity, respectively. In the spin density wave(SDW) state, the QPI pattern exhibits a dimer structure in the energy region of the SDW gap, with its orientation along the ferromagnetic direction of the SDW order. When the energy is increased to be near the Fermi level, it exhibits two sets of dimers along the same direction. The dimer structure of the QPI patterns persists with the decrease of the SDW correlation length in the magnetic driven nematic phase, although it tends to merge together for the scattering patterns with energies close to the Fermi level. While in the orbital scenario, the QPI patterns exhibit a dimer structure in a wide energy region. It undergoes a {\pi}/2 rotation with the increasing of energy, which is associated with the inequivalent energies of the two Dirac nodes induced by the orbital order. These distinct features may be used to probe or distinguish two kinds of scenarios of the nemeticity., Comment: updated to the published version

By using scanning tunneling microscopy (STM) / spectroscopy (STS), we systematically characterize the electronic structure of lightly doped 1T-TiSe2, and demonstrate the existence of the electronic inhomogeneity and the pseudogap state. It is found that the intercalation induced lattice distortion impacts the local band structure and reduce the size of the charge density wave (CDW) gap with the persisted 2x2 spatial modulation. On the other hand, the delocalized doping electrons promote the formation of pseudogap. Domination by either of the two effects results in the separation of two characteristic regions in real space, exhibiting rather different electronic structures. Further doping electrons to the surface confirms that the pseudogap may be the precursor for the superconducting gap. This study suggests that the competition of local lattice distortion and the delocalized doping effect contribute to the complicated relationship between charge density wave and superconductivity for intercalated 1T-TiSe2., Comment: 12 pages, 5 figures

We study the possible superconducting pairing symmetry mediated by spin and charge fluctuations on the honeycomb lattice using the extended Hubbard model and the random-phase-approximation method. From $2\%$ to $20\%$ doping levels, a spin-singlet $d_{x^{2}-y^{2}}+id_{xy}$-wave is shown to be the leading superconducting pairing symmetry when only the on-site Coulomb interaction $U$ is considered, with the gap function being a mixture of the nearest-neighbor and next-nearest-neighbor pairings. When the offset of the energy level between the two sublattices exceeds a critical value, the most favorable pairing is a spin-triplet $f$-wave which is mainly composed of the next-nearest-neighbor pairing. We show that the next-nearest-neighbor Coulomb interaction $V$ is also in favor of the spin-triplet $f$-wave pairing., Comment: 6 pages, 4 figures

The Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) unconventional superconductors attract renewed interest in recent years. However, an unambiguous experimental demonstration of the FFLO state is hindered by the stringent requirements for its realization. In this paper, we explore the relationship between the magnetic frustration and the emergence of the FFLO state on an anisotropic triangular lattice, based on the self-consistent calculation of the Bogoliubov-de Gennes equations. We find that the required lower critical magnetic field to enter the FFLO state decreases with the increase of both the anisotropic ratio and the on-site Coulomb repulsive interaction. This demonstrates that it is easier to enter the FFLO state on the structurally frustrated triangular lattice in comparison with the square lattice, and suggests that the layered organic superconductors with a triangular lattice may be good candidates for exploring the FFLO state.

Sn4+-doped V2O5 cathode materials were prepared by a sol–gel method. The results showed that the modified cathode material was a mixture of V4+ and V5+. It was a kind of typical mesopore material with pores of 2–4 nm diameter. Symmetrical curves were obtained by cyclic voltammetry (CV) tests performed at different scanning rates and voltage ranges. In particular, the CV curve showed more obvious rectangle property and better redox properties when the scanning rate was 5 mV s−1. At the current density of 200 mA g−1, the maximum specific energy, specific power, and coulomb efficiency of the material were 27.25 mA h g−1, 494.87 W kg−1, and 97%, respectively. It was indicated that small amounts of Sn4+ doping would improve the surface morphology and electronic conductivity of V2O5. The Sn4+-doped V2O5 showed good capacitance characteristics.

In this paper, we examine the effect on spin dynamics of three kinds of possible superconducting (SC) gap in electron-doped high- T c systems, that is, the d x 2 - y 2 -wave, the mixed d x 2 - y 2 + higher d -wave harmonics ( cos ( 6 ϕ ) ) , and the d x 2 - y 2 + is -wave. Starting from the slave-boson mean-field approach to the t - t ′ - J model, a higher d -wave gap term and an is -wave component are included in a phenomenological form, respectively. With the random-phase approximation (RPA), we present a detailed analysis of the momentum, frequency and doping dependence of the spin susceptibility. It is found that at low frequencies, the spin response is commensurate in the SC state and there is a crossover frequency ω c above which the spin response begins to be incommensurate, and the crossover frequency ω c increases with doping. So the dispersion of the excitation is different from the hole-doped cuprates, in which a hourglass-like dispersion is observed. We also find that a spin resonance appears in the underdoped and optimally doped regime. These similar characters for the three kinds of superconducting gap suggest the underlying importance of Fermi surface (FS) topology. On the other hand, the incommensurate spin fluctuation at high frequencies is found to exhibit a ring structure around ( π , π ) for the mixed cos ( 2 ϕ ) + cos ( 6 ϕ ) -wave, while others show maxima along the ( π , π + δ π ) and its symmetric directions. Below ω c , the spin response remains to be commensurate all along to the lowest frequency for the d x 2 - y 2 + is -wave, while the others cross to a small incommensurate structure with further decreasing the frequency. These may be taken to probe the possible subdominant SC components.

The effect of a magnetic field parallel to the CuO2 plane on the Raman spectra is investigated based on the Slave–Boson approach to the t − t′ − J model with a Zeeman field and the random-phase approximation. We find that the Raman spectra intensities in the superconducting (SC) state are suppressed for both the B1g and the B2g channels with a slight shift of the peaks position toward lower frequency in the B1g channel and a negligible shift in the B2g channel due to the Zeeman splitting. There is a field-induced peak and dip structure at low energy response in the B2g channel at very low temperature. While rising temperature has a similar effect in reducing the Raman response peak in the superconducting (SC) state, it smears out the field-induced peak and dip structure in the B2g channel. We compare these results with experiments and give explanations based on the field-induced changes of the density of the superconducting condensate, the momentum distribution of the quasiparticle energy and the scattering rate.

Motivated by recent experimental measurements, we study the quasiparticle spectra and the collective excitations in doped ${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$, in which the interesting interplay between the electronic correlations and strong spin-orbital coupling (SOC) exists. To include the SOC, we use the Hugenholtz diagrams to extend the fluctuation exchange (FLEX) approach to the case where the SU(2) symmetry can be broken. By using this generalized FLEX method, we find a weak pseudogap behavior near $(\ensuremath{\pi},0)$ in the slightly electron-doped system, with the corresponding Fermi arc formed by the partial destruction of Fermi surface. Similar features also appear in the hole-doped system; however, the position of the Fermi arc is rotated ${45}^{\ensuremath{\circ}}$ with respect to the former. These results are consistent with the recent angle-resolved photoemission spectra in ${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$. We suggest that these anomalous phenomena are caused by the scatterings of quasiparticles off the isospin fluctuation derived from the effective ${J}_{\text{eff}}=1/2$ doublet.

This study describes the development of novel protocols extending the real-time ultrasonic reflectometry(UTDR) for the detection of membrane fouling in hollow fiber module during ultrafiltration(UF) of oily water treatment. A specially designed acoustic sensor with a frequency of 2.5 MHz was used. The hollow fiber membranes used were polysulphone(PSf) UF membranes with MWCO 40 kDa. The wastewaters with three different oily concentrations of 100, 500 and 1 000 mg/L were investigated. Diesel oil was utilized as the primary foulant. The results show that the permeate flux declines with operation time and its value becomes lower with the increase of the oily concentration in wastewater. It is found that ultrasonic measurement can detect the fouling and cleaning processes. A new signal analysis protocol—ultrasonic reflected energy was developed. Ultrasonic reflected energy obtained indicates the deposition of oily layer as a function of operation time and its removal after cleaning. The overall flux decline is reasonably correlated with the changes in ultrasonic reflected energy. This research provides the evidence that the ultrasonic reflectometry technique is capable of monitoring membrane fouling and cleaning in hollow fiber modules.

One of the greatest challenges in membrane fouling studies is the development of non-invasive methods that allow for in situ detection of protein fouling, especially in tubular membrane modules. This study describes the extension of ultrasonic time-domain reflectometry (UTDR) for the real-time measurement of protein fouling on tubular ultrafiltration (UF) membranes. A specially designed focused transducer with a frequency of 7.5 MHz was used in this study. The tubular membrane was a polyethersulphone (PES) UF membrane with MWCO 40 kDa. The feed used was 0.08 and 3 g/l bovine serum albumin (BSA) solutions. The results show that the UTDR technique can distinguish and recognize the acoustic response signals from the various curve surfaces of the housing holder, steel support and membrane within a tubular membrane module. Changes in the amplitude of the differential signals obtained provide useful quantitative information about the deposited BSA on the membrane. A linear relationship between the amplitude of the observed signals and fouling resistance exists in the fouling experiment with 0.08 g/l BSA. The rate at which the ultrasonic amplitude increased became faster at fouling operation with 3 g/l BSA than with 0.08 g/l BSA. Flux measurements and UV analysis corroborate the ultrasonic testing.

Motivated by the recent atomic-scale scanning tunneling microscope (STM) observation for a spatially localized in-gap state in an electron doped Mott insulator, we evaluate the local electronic state of the Hubbard model on the square lattice using the cluster perturbation theory. An in-gap state is found to exist below the upper Hubbard band around the dopant lattice site, which is consistent with the STM measurements. The emergence of this local in-gap state is accompanied with a rapid reduction of the double occupancy of electrons. A similar in-gap state is also found to exist on the triangular lattice. These results suggest that the in-gap state is an inherent feature of Mott insulators independent of the lattice structure.

Electronic Raman spectra in high-Tc superconductors are studied based on the slave-boson approach to the t–t′–J model and by including antiferromagnetic spin fluctuations via the renormalized random-phase approximation. It is found that antiferromagnetic spin fluctuations affect largely the A1g spectrum, but less effectively the B2g spectrum. A low-frequency peak in the A1g channel, which is at the experimental value, is ascribed to coming from the coupling to the spin resonance mode. The doping dependence of the B2g peak is shown to be consistent with experiments. The effect of spin fluctuations on the B1g spectrum is also discussed.

The spectra observed in angle-resolved photoemission spectroscopy measurements are examined together with the resonance peak observed in neutron scattering, based on the slave-boson approach to the $t\ensuremath{-}{t}^{\ensuremath{'}}\ensuremath{-}J$ model. We show that the peak/dip/hump features arise from the scattering of electrons by collective spin excitations which, at the same time, give rise to the neutron resonance mode. The doping dependences and the dispersions of the peak/dip/hump positions are shown to be consistent with experiments. The recently observed $\mathrm{cos}(6\ensuremath{\theta})$ deviation from the pure d wave is also discussed based on the renormalization by spin fluctuations.

Charge fluctuations are investigated in a ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$-wave superconductor. Using a $t\ensuremath{-}{t}^{\ensuremath{'}}$ tight-binding band, twin peaks show up around the incommensurate $\mathbf{q}=(\ensuremath{\pi}\ifmmode\pm\else\textpm\fi{}{\ensuremath{\delta}}_{0},\ensuremath{\pi}\ifmmode\pm\else\textpm\fi{}{\ensuremath{\delta}}_{0})$ and $(\ensuremath{\pi}\ifmmode\pm\else\textpm\fi{}{\ensuremath{\delta}}_{0},\ensuremath{\pi}\ensuremath{\mp}{\ensuremath{\delta}}_{0})$ at low frequencies which shift to $\mathbf{q}=(\ensuremath{\pi},\ensuremath{\pi}\ifmmode\pm\else\textpm\fi{}\ensuremath{\delta})$ and $(\ensuremath{\pi}\ifmmode\pm\else\textpm\fi{}\ensuremath{\delta},\ensuremath{\pi})$ when the frequency is above a threshold ${\ensuremath{\omega}}_{1}.$ When the frequency is above another threshold ${\ensuremath{\omega}}_{2} (g{\ensuremath{\omega}}_{1}),$ more intense peaks appear at $\mathbf{q}=(\ensuremath{\pi}\ifmmode\pm\else\textpm\fi{}{\ensuremath{\delta}}^{\ensuremath{'}},\ensuremath{\pi}\ifmmode\pm\else\textpm\fi{}{\ensuremath{\delta}}^{\ensuremath{'}})$ and $(\ensuremath{\pi}\ifmmode\pm\else\textpm\fi{}{\ensuremath{\delta}}^{\ensuremath{'}},\ensuremath{\pi}\ensuremath{\mp}{\ensuremath{\delta}}^{\ensuremath{'}}).$ These incommensurate charge fluctuations have fairly distinct features when comparing to spin fluctuations and are fundamentally different from what should occur in a charge stripe phase.

The title compound, C23H18O4, contains two mol­ecules in the asymmetric unit which differ from each other in the dihedral angles between the benzyl and chromone groups. There are intra­molecular and inter­molecular C—H⋯O inter­actions as well as π–π stacking inter­actions in the crystal structure.

The differences between the magnetic properties in the normal state of the underdoped and optimally doped high-Tc cuprates are discussed based on a phenomenological model, in which the effect of the spin gap on the magnetic susceptibility is included. The closely related temperature dependences of the uniform static spin susceptibility, the spin-lattice relaxation rate at the planar O sites 17(T1T)−1 and Cu sites 63(T1T)−1, and the ratio of 63(T1T)−1 to the squared Gaussian relaxation rate at the planar Cu sites T2G−2 are considered. The theoretical predictions are in agreement with experiments.

Using an extension of the Jordan - Wigner transformation (JWT) in two dimensions, the effects of weak interchain coupling on the spin - Peierls (SP) system is studied. The magnetic interaction is considered to be a quantum XY-interaction, and the spin - lattice distortion is treated quasiclassically. On the analogy of the stepped Peierls transition theory, we propose a stepped SP transition theory. We find that, when any finite transverse coupling is introduced between nearest chains, the usual SP transition will be modified, and the dimerization and the opening of the gap will no longer occur simultaneously. This leads to the appearance of a gapless SP phase over a certain temperature region.

An explanation of the closely related temperature dependences of both charge and spin excitations in the CuO 2 plane for underdoped YBCO systems is presented. The spin pseudogap and the anomalous temperature dependences of the in-plane resistivity and the optical conductivity observed in these underdoped compounds are suggested to follow from the energy difference between the chemical potential and the energy of hole quasiparticles at the van Hove singularity (vHs). The numerical results based on the quasiparticle spectrum calculated by Dagatto et al. [Phys. Rev. Lett. 74 (1995) 310] are in good agreement with experiments.

The effect of pre-existing acid-base proton transfer on ion formation in secondary ion mass spectrometry (SIMS) is studied with model systems constructed by Langmuir-Blodgett techniques. Reflection-Absorption FTIR was used to verify proton transfer in tri-layer LB assemblies of docosanoic acid (A) and 1-docosylamine (B). A recently developed quantitative method for quasi-molecular ions in Static SIMS was extended to Time-of-Flight SIMS. The formation of protonated base ions ((B + H)+) is highly dependent on film structure and pre-existing chemistry. The formation of the conjugate (A−H)−) carboxylate anion is more dependent on concentration of species rather than local chemistry. The implications for molecular quantitative analysis in SIMS are discussed.

Spin and hole excitations are investigated in the doped two-dimensional (2D) antiferromagnets described by the [ital t]-[ital J] model based on the spin-wave approximation. The polarizability of spin excitations is found to be consistent with the marginal-Fermi-liquid hypothesis. As a consequence, the imaginary part of the self-energy for holes scattered by the spin excitations is demonstrated to give a linear dependence in temperature [ital T] (for [omega][lt][ital T]) and in frequency [omega] (for [omega][gt][ital T]).

We study the electronic instabilities of the Hubbard model in the 1/6 hole-doped Kagome lattice using the variational cluster approach. The 1/6 hole doping is unique in the sense that the Fermi level is at the van Hove singularity and the Fermi surface has a perfect nesting. In this case, a density wave is usually realized. However, we demonstrate here that the chiral ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}+i{d}_{xy}$ superconducting state is most favorable when a small Hubbard interaction $U$ ($Ul3.0t$) is introduced, and a scalar chiral spin order is realized at large $U$ ($Ug5.5t$). Between them, a spin-disordered insulating state is proposed.

We investigate the pairing symmetry in heavily overdoped Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$ based on the spin-fluctuation mechanism. The exotic octet nodes of the superconducting gap and the unusual evolution of the gap with doping observed by the recent experiments are well explained in a unified manner. We demonstrate that the scatterings of electrons on the Fermi patches is mainly responsible for the incommensurate spin fluctuations and consequently the Fermi-surface-dependent multi-gap structure, since the Fermi level is close to the flat band. In addition, we find that a $d$-wave pairing state will prevail over the s-wave pairing state around the Lifshitz transition point., Comment: 7 pages, 4 figures

The quasiparticle spectra of the Hubbard model on the anisotropic triangle lattice at half filling is studied using the cluster perturbation theory and applied to the organic superconductor kappa-(BEDT-TTF)(2)X. We find that a d(x2-y2)-wave-like pseudogap phase emerges in the intermediate-coupling regime. Near the critical line of the Mott insulating transition, the Fermi surface becomes segmented with a Fermi arc, due to the partial opening of the Mott gap along the Fermi surface. The pseudogap with the Fermi arc is shown to be a precursor to the Mott insulator.

The effects of magnetic vortices and nonmagnetic impurities on the low energy quasiparticle excitations and the spin-lattice relaxation rate are examined in the iron-based superconductors for the $s_{\pm}$-, $s$- and d-wave pairing symmetries, respectively. The main effect of the vortices is to enhance the quasiparticle excitations and the spin-lattice relaxation rate for all symmetries, and leads to a $T^{3}$ dependence of the relaxation rate followed by a nearly $T$-linearity at lower temperatures. This enhancement can only be seen for the $s_{\pm}$- and d-wave symmetries in the presence of nonmagnetic impurities. These results suggest that the $s_{\pm}$-wave and d-wave pairing states behave similarly in response to the magnetic field and nonmagnetic impurities, therefore it may be impossible to distinguish them on the basis of the measurements of spin-lattice relaxation rates when a magnetic field and/or impurity scatterings are present., 7 pages, 5 figures