Multipole polaron in the devil's staircase of CeSb

Rare-earth intermetallic compounds exhibit rich phenomena induced by the interplay between localized f orbitals and conduction electrons. However, since the energy scale of the crystal-electric-field splitting is only a few millielectronvolts, the nature of the mobile electrons accompanied by collective crystal-electric-field excitations has not been unveiled. Here, we examine the low-energy electronic structures of CeSb through the anomalous magnetostructural transitions below the Néel temperature, ~17 K, termed the 'devil's staircase', using laser angle-resolved photoemission, Raman and neutron scattering spectroscopies. We report another type of electron-boson coupling between mobile electrons and quadrupole crystal-electric-field excitations of the 4f orbitals, which renormalizes the Sb 5p band prominently, yielding a kink at a very low energy (~7 meV). This coupling strength is strong and exhibits anomalous step-like enhancement during the devil's staircase transition, unveiling a new type of quasiparticle, named the 'multipole polaron', comprising a mobile electron dressed with a cloud of the quadrupole crystal-electric-field polarization.

Magnetic structures and electronic properties of cubic-pyrochlore ruthenates from first principles

The magnetic ground states ofR₂Ru₂O₇andA₂Ru₂O₇withR= Pr, Gd, Ho, and Er, as well asA= Ca, Cd are predicted devising a combination of the cluster-multipole (CMP) theory and spin-density-functional theory (SDFT). The strong electronic correlation effects are estimated by the constrained-random-phase approximation (cRPA) and taken into account within the dynamical-mean-field theory (DMFT). The target compounds feature d-orbital magnetism on Ru⁴⁺and Ru⁵⁺ions forRandA, respectively, as well as f-orbital magnetism on theRsite, which leads to an intriguing interplay of magnetic interactions in a strongly correlated system. We find CMP + SDFT is capable of describing the magnetic ground states in these compounds. The cRPA captures a difference in the screening strength betweenR₂Ru₂O₇andA₂Ru₂O₇compounds, which leads to a qualitative and quantitative understanding of the electronic properties within DMFT.

Topological Kagome Magnet Co3Sn2S2 Thin Flakes with High Electron Mobility and Large Anomalous Hall Effect

Magnetic Weyl semimetals attract considerable interest not only for their topological quantum phenomena but also as an emerging materials class for realizing quantum anomalous Hall effect in the two-dimensional limit. A shandite compound Co₃Sn₂S₂ with layered kagome-lattices is one such material, where vigorous efforts have been devoted to synthesize the two-dimensional crystal. Here, we report a synthesis of Co₃Sn₂S₂ thin flakes with a thickness of 250 nm by chemical vapor transport method. We find that this facile bottom-up approach allows the formation of large-sized Co₃Sn₂S₂ thin flakes of high-quality, where we identify the largest electron mobility (∼2600 cm² V^-1 s^-1) among magnetic topological semimetals, as well as the large anomalous Hall conductivity (∼1400 Ω^-1 cm^-1) and anomalous Hall angle (∼32%) arising from the Berry curvature. Our study provides a viable platform for studying high-quality thin flakes of magnetic Weyl semimetal and stimulate further research on unexplored topological phenomena in the two-dimensional limit.

Giant magneto-optical responses in magnetic Weyl semimetal Co3Sn2S2

The Weyl semimetal (WSM), which hosts pairs of Weyl points and accompanying Berry curvature in momentum space near Fermi level, is expected to exhibit novel electromagnetic phenomena. Although the large optical/electronic responses such as nonlinear optical effects and intrinsic anomalous Hall effect (AHE) have recently been demonstrated indeed, the conclusive evidence for their topological origins has remained elusive. Here, we report the gigantic magneto-optical (MO) response arising from the topological electronic structure with intense Berry curvature in magnetic WSM Co₃Sn₂S₂. The low-energy MO spectroscopy and the first-principles calculation reveal that the interband transitions on the nodal rings connected to the Weyl points show the resonance of the optical Hall conductivity and give rise to the giant intrinsic AHE in dc limit. The terahertz Faraday and infrared Kerr rotations are found to be remarkably enhanced by these resonances with topological electronic structures, demonstrating the novel low-energy optical response inherent to the magnetic WSM.

Publisher Correction: A weak topological insulator state in quasi-one-dimensional bismuth iodide

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Devil's staircase transition of the electronic structures in CeSb

Solids with competing interactions often undergo complex phase transitions with a variety of long-periodic modulations. Among such transition, devil's staircase is the most complex phenomenon, and for it, CeSb is the most famous material, where a number of the distinct phases with long-periodic magnetostructures sequentially appear below the Néel temperature. An evolution of the low-energy electronic structure going through the devil's staircase is of special interest, which has, however, been elusive so far despite 40 years of intense research. Here, we use bulk-sensitive angle-resolved photoemission spectroscopy and reveal the devil's staircase transition of the electronic structures. The magnetic reconstruction dramatically alters the band dispersions at each transition. Moreover, we find that the well-defined band picture largely collapses around the Fermi energy under the long-periodic modulation of the transitional phase, while it recovers at the transition into the lowest-temperature ground state. Our data provide the first direct evidence for a significant reorganization of the electronic structures and spectral functions occurring during the devil's staircase.

Large Variation of Dirac Semimetal State in Perovskite CaIrO_{3} with Pressure-Tuning of Electron Correlation

The impact of electron correlation on the Dirac semimetal state is investigated for perovskite CaIrO_{3} in terms of the magnetotransport properties under varying pressures. The reduction of electron correlation with a pressure of 1 GPa enhances the Fermi velocity as much as 40%, but it reduces the mobility by an order of magnitude by detuning the Dirac node from the Fermi energy. Moreover, the giant magnetoresistance at the quantum limit due to the one-dimensional confinement of Dirac electrons is critically suppressed under pressure. These results indicate that the electron correlation is a crucial knob for controlling the transport of a correlated Dirac semimetal.

Strong-correlation induced high-mobility electrons in Dirac semimetal of perovskite oxide

Electrons in conventional metals become less mobile under the influence of electron correlation. Contrary to this empirical knowledge, we report here that electrons with the highest mobility ever found in known bulk oxide semiconductors emerge in the strong-correlation regime of the Dirac semimetal of perovskite CaIrO₃. The transport measurements reveal that the high mobility exceeding 60,000 cm²V⁻¹s⁻¹ originates from the proximity of the Fermi energy to the Dirac node (ΔE < 10 meV). The calculation based on the density functional theory and the dynamical mean field theory reveals that the energy difference becomes smaller as the system approaches the Mott transition, highlighting a crucial role of correlation effects cooperating with the spin-orbit coupling. The correlation-induced self-tuning of Dirac node enables the quantum limit at a modest magnetic field with a giant magnetoresistance, thus providing an ideal platform to study the novel phenomena of correlated Dirac electron.

Electron correlation normally makes electrons less mobile, but it is still not clear when correlation becomes very strong in Dirac semimetals. Here, Fujioka et al. report a very high electron mobility exceeding 60,000 cm²V⁻¹s⁻¹ in correlated Dirac semimetal of perovskite CaIrO3, due to the enhanced electron correlation nearby the Mott transition.

Multiple-q noncollinear magnetism in an itinerant hexagonal magnet

Multiple-q spin order, i.e., a spin texture characterized by a multiple number of coexisting magnetic modulation vectors q, has recently attracted attention as a source of nontrivial magnetic topology and associated emergent phenomena. One typical example is the triple-q skyrmion lattice state stabilized by Dzyaloshinskii-Moriya interactions in noncentrosymmetric magnets, while the emergence of various multiple-q states of different origins is expected according to the latest theories. Here, we investigated the magnetic structure of the itinerant polar hexagonal magnet Y₃Co₈Sn₄, in which several distinctive mechanisms favoring multiple-q states are allowed to become active. Small-angle neutron-scattering experiments suggest the formation of incommensurate triple-q magnetic order with an in-plane vortex-like spin texture, which can be most consistently explained in terms of the novel four-spin interaction mechanism inherent to itinerant magnets. The present results suggest a new route to realizing exotic multiple-q orders and that itinerant hexagonal magnets, including the R ₃ M ₈Sn₄ family with wide chemical tunability, can be a unique material platform to explore their rich phase diagrams.

Magnetic order of Nd5Pb3 single crystals

We report millimeter-sized Nd₅Pb₃ single crystals grown out of a Nd-Co flux. We experimentally study the magnetic order of Nd₅Pb₃ single crystals by measuring the anisotropic magnetic properties, electrical resistivity under high pressure up to 8 GPa, specific heat, and neutron single crystal diffraction. Two successive magnetic orders are observed at T _N1  =  44 K and T _N2  =  8 K. The magnetic cells can be described with a propagation vector [Formula: see text]. Cooling below T _N1, Nd1 and Nd3 order forming ferromagnetic stripes along the b-axis, and the ferromagnetic stripes are coupled antiferromagnetically along the a-axis for the [Formula: see text] magnetic domain. Cooling below T _N2, Nd2 orders antiferromagnetically to nearby Nd3 ions. All ordered moments align along the crystallographic c-axis. The magnetic order at T _N1 is accompanied by a quick drop of electrical resistivity upon cooling and a lambda-type anomaly in the temperature dependence of specific heat. At T _N2, no anomaly was observed in electrical resistivity but there is a weak feature in specific heat. The resistivity measurements under hydrostatic pressures up to 8 GPa suggest a possible phase transition around 6 GPa. Our first-principles band structure calculations show that Nd₅Pb₃ has the same electronic structure as does Y₅Si₃ which has been reported to be a one-dimensional electride with anionic electrons that do not belong to any atom. Our study suggests that R ₅Pb₃ (R  =  rare earth) can be a materials playground for the study of magnetic electrides. This deserves further study after experimental confirmation of the presence of anionic electrons.

Evidence for magnetic Weyl fermions in a correlated metal

Weyl fermions have been observed as three-dimensional, gapless topological excitations in weakly correlated, inversion-symmetry-breaking semimetals. However, their realization in spontaneously time-reversal-symmetry-breaking phases of strongly correlated materials has so far remained hypothetical. Here, we report experimental evidence for magnetic Weyl fermions in Mn₃Sn, a non-collinear antiferromagnet that exhibits a large anomalous Hall effect, even at room temperature. Detailed comparison between angle-resolved photoemission spectroscopy (ARPES) measurements and density functional theory (DFT) calculations reveals significant bandwidth renormalization and damping effects due to the strong correlation among Mn 3d electrons. Magnetotransport measurements provide strong evidence for the chiral anomaly of Weyl fermions-namely, the emergence of positive magnetoconductance only in the presence of parallel electric and magnetic fields. Since weak magnetic fields (approximately 10 mT) are adequate to control the distribution of Weyl points and the large fictitious fields (equivalent to approximately a few hundred T) produced by them in momentum space, our discovery lays the foundation for a new field of science and technology involving the magnetic Weyl excitations of strongly correlated electron systems such as Mn₃Sn.

Orbital-Dependent Band Narrowing Revealed in an Extremely Correlated Hund's Metal Emerging on the Topmost Layer of Sr_{2}RuO_{4}

We use a surface-selective angle-resolved photoemission spectroscopy and unveil the electronic nature on the topmost layer of Sr_{2}RuO_{4} crystal, consisting of slightly rotated RuO_{6} octahedrons. The γ band derived from the 4d_{xy} orbital is found to be about three times narrower than that for the bulk. This strongly contrasts with a subtle variation seen in the α and β bands derived from the one-dimensional 4d_{xz/yz}. This anomaly is reproduced by the dynamical mean-field theory calculations, introducing not only the on-site Hubbard interaction but also the significant Hund's coupling. We detect a coherence-to-incoherence crossover theoretically predicted for Hund's metals, which has been recognized only recently. The crossover temperature in the surface is about half that of the bulk, indicating that the naturally generated monolayer of reconstructed Sr_{2}RuO_{4} is extremely correlated and well isolated from the underlying crystal.

Vascular Normalization by ROCK Inhibitor: Therapeutic Potential of Ripasudil (K-115) Eye Drop in Retinal Angiogenesis and Hypoxia

PURPOSE

In this study, we investigated the therapeutic potential of a Rho-associated coiled-coil-containing protein kinase (ROCK) inhibitor ripasudil (K-115) eye drop on retinal neovascularization and hypoxia.

METHODS

In vitro, human retinal microvascular endothelial cells (HRMECs) were pretreated with ripasudil and then stimulated with VEGF. ROCK activity was evaluated by phosphorylation of myosin phosphatase target protein (MYPT)-1. Endothelial migration and cell viability were assessed by cell migration and MTT assay, respectively. The concentration of ripasudil in the retina was measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In vivo, normal saline, 0.4%, or 0.8% ripasudil were administered three times a day to mice with oxygen-induced retinopathy (OIR). The areas of neovascularization and avascular retina were also quantified with retinal flat-mounts at postnatal day (P) 15, P17, or P21. The retinal hypoxic area was evaluated using hypoxia-sensitive drug pimonidazole by immunohistochemistry at P17. The vascular normalization was also evaluated by immunohistochemistry at P17.

RESULTS

Ripasudil but not fasudil significantly reduced VEGF-induced MYPT-1 phosphorylation in HRMECs at 30 μmol/L. Ripasudil significantly inhibited VEGF-induced HRMECs migration and proliferation. The concentration of ripasudil in the retina was 3.8 to 10.4 μmol/L and 6.8 to 14.8 μmol/L after 0.4% and 0.8% ripasudil treatment, respectively. In the 0.4% and 0.8% ripasudil treated OIR mice, the areas of neovascularization as well as avascular area in the retina was significantly reduced compared with those of saline-treated mice at P17 and P21. Pimonidazole staining revealed that treatment with 0.4% and 0.8% ripasudil significantly inhibited the increase in the hypoxic area compared with saline. 0.8% ripasudil could cause intraretinal vascular sprouting and increase retinal vascular perfusion.

CONCLUSIONS

Novel ROCK inhibitor ripasudil eye drop has therapeutic potential in the treatment of retinal hypoxic neovascular diseases via antiangiogenic effects as well as vascular normalization.

Wide-field laser ophthalmoscopy for imaging of gas-filled eyes after macular hole surgery

BACKGROUND AND OBJECTIVE

Existing ophthalmoscopy methods are unable to obtain clear fundus autofluorescence (FAF) images in gas-filled eyes. The purpose of this study was to evaluate the capability of wide-field laser ophthalmoscopy (Optos) in obtaining FAF images in gas-filled eyes for the assessment of macular hole (MH) closure after surgery.

METHODS

This was an interventional case series. Eighteen consecutive patients with unilateral MH underwent vitrectomy with internal limiting membrane peeling and 20% sulfur hexafluoride gas tamponade. FAF images using Optos were recorded preoperatively and postoperatively (days 1, 2, and 7).

RESULTS

On postoperative days 1, 2, and 7, FAF images were obtained from 11/18 (61.1%), 9/18 (50.0%), and 17/18 eyes (94.4%), respectively, using Optos. The quality of FAF images using Optos was sufficient to determine MH closure in 9/18 (50.0%) of gas-filled eyes postoperatively. Quantitative analysis of FAF images was helpful in determining complete or partial closure of the MH.

CONCLUSION

FAF imaging using Optos might be a useful adjunct to optical coherence tomography as a supportive method to guide the release from facedown posturing in some cases of MH.

Clinical Features of Systemic Metastatic Retinal Lymphoma in Japanese Patients

PURPOSE

Systemic metastatic retinal lymphoma (SMRL) originates in systemic organs. It has been reported to exhibit clinical features similar to those of primary vitreoretinal lymphoma (PVRL). We report six cases of SMRL in a single-center survey in Japan.

METHODS

The clinical and pathologic features in SMRL at the Kyushu University Hospital were retrospectively studied.

RESULTS

The mean patient age at the onset of ocular involvement was 75.3 years. Four patients had brain involvement. The primary sites were: breast (2); chest (1); testis (1); intestinal tract (1); and nasal sinus (1). In all patients, the cytology of vitreous samples indicated diffuse large B-cell lymphoma (DLBCL).

CONCLUSIONS

DLBCL is the most common subtype in our study. The prevalence of CNS involvement in patients with SMRL is similar to that with PVRL. The testis and breast may be common sites of origin for SMRL.

Distinct Profiles of Soluble Cytokine Receptors Between B-Cell Vitreoretinal Lymphoma and Uveitis

PURPOSE

To determine the profiles of soluble cytokine receptors and cytokines, including mostly their ligands, in the vitreous humor of patients with B-cell vitreoretinal lymphoma (VRL) and uveitis.

METHODS

Vitreous samples were collected from immunocompetent patients with VRL (n = 21), uveitis (n = 20), and idiopathic epiretinal membrane (n = 21) as controls. Cytometric beads assay were used to determine the vitreous concentrations of soluble receptors and cytokines.

RESULTS

Vitreous levels of soluble IL-2 receptor α (sIL-2Rα), sIL-6R, soluble tumor necrosis factor receptor (TNFR) 1, sTNFR2, soluble vascular endothelial growth factor receptor (sVEGFR) 1, sVEGFR2, and IL-10 were higher in patients with VRL than in those with uveitis and controls, whereas those of sIL-1R1, sIL-1R2, and sIL-4R were higher in patients with uveitis than those with VRL and controls. In analyses in patients with VRL, elevation of sVEGFR1 and sVEGFR2 levels was more prominent in patients with systemic metastatic retinal lymphoma (SMRL) than in those with primary VRL/primary central nervous system lymphoma (PVRL/PCNSL). Furthermore, sIL-2Rα levels were increased in patients with VRL who developed subretinal lesions compared with in those who mainly had vitreous cavity opacity, positively correlated with the density of CD3+ cells in the vitrectomy cell blocks.

CONCLUSIONS

The profiles of soluble cytokine receptors and cytokines in patients with VRL were different from those with uveitis. In addition, sVEGFR1 and sVEGFR2 levels may be differential diagnostic markers between PVRL/PCNSL and SMRL, and sIL-2Rα levels can anticipate infiltration of VRL cells into the subretina and/or retina.

ROCK-isoform-specific polarization of macrophages associated with age-related macular degeneration

Age is a major risk factor in age-related macular degeneration (AMD), but the underlying cause is unknown. We find increased Rho-associated kinase (ROCK) signaling and M2 characteristics in eyes of aged mice, revealing immune changes in aging. ROCK isoforms determine macrophage polarization into M1 and M2 subtypes. M2-like macrophages accumulated in AMD, but not in normal eyes, suggesting that these macrophages may be linked to macular degeneration. M2 macrophages injected into the mouse eye exacerbated choroidal neovascular lesions, while M1 macrophages ameliorated them, supporting a causal role for macrophage subtypes in AMD. Selective ROCK2 inhibition with a small molecule decreased M2-like macrophages and choroidal neovascularization. ROCK2 inhibition upregulated M1 markers without affecting macrophage recruitment, underlining the plasticity of these macrophages. These results reveal age-induced innate immune imbalance as underlying AMD pathogenesis. Targeting macrophage plasticity opens up new possibilities for more effective AMD treatment.

Increased vitreous concentrations of MCP-1 and IL-6 after vitrectomy in patients with proliferative diabetic retinopathy: possible association with postoperative macular oedema

PURPOSE

To determine whether vitreal concentrations of MCP-1, IL-6 and IL-8 are altered after vitrectomy in patients with proliferative diabetic retinopathy (PDR) and to investigate whether the altered levels of these cytokines are associated with postoperative macular oedema.

METHODS

Vitreous samples were collected from 36 eyes of 33 patients with PDR before pars plana vitrectomy without intraocular lens (IOL) implantation, and also from the same 36 eyes during IOL implantation surgery approximately 7 months after the initial vitrectomy. Levels of MCP-1, IL-6, IL-8 and vascular endothelial growth factor were measured by flow cytometry using cytometric bead array (CBA) technology.

RESULTS

The mean vitreous levels of MCP-1, IL-6 and IL-8 in the samples collected before vitrectomy were significantly higher in patients with PDR than in control patients (p<0.0001). The levels of MCP-1 and IL-6 in the samples collected at the time of IOL implantation were significantly higher than those collected before vitrectomy (p<0.05). In contrast, the level of IL-8 was significantly lower after vitrectomy (p<0.05). The levels of IL-6 and IL-8, but not MCP-1, in the vitreous from eyes with PDR were inversely correlated with the interval between the initial vitrectomy and the time of implantation surgery. Among the vitrectomised patients, the mean vitreous level of MCP-1 in eyes with diabetic macular oedema (DME) was significantly higher than in those without DME (p=0.028).

CONCLUSIONS

The elevated levels of MCP-1 and IL-6 may indicate prolonged inflammation even after successful vitrectomy, which can cause postoperative DME.

Anisotropy of the superconducting gap in the iron-based superconductor BaFe2(As(1-x)P(x))2

We report peculiar momentum-dependent anisotropy in the superconducting gap observed by angle-resolved photoemission spectroscopy in BaFe₂(As_1-xP_x)₂ (x = 0.30, T_c = 30 K). Strongly anisotropic gap has been found only in the electron Fermi surface while the gap on the entire hole Fermi surfaces are nearly isotropic. These results are inconsistent with horizontal nodes but are consistent with modified s_± gap with nodal loops. We have shown that the complicated gap modulation can be theoretically reproduced by considering both spin and orbital fluctuations.

Increased expression of M-CSF and IL-13 in vitreous of patients with proliferative diabetic retinopathy: implications for M2 macrophage-involving fibrovascular membrane formation

PURPOSE

We recently demonstrated that M2 macrophages were involved in the development of fibrovascular membranes (FVM) associated with proliferative diabetic retinopathy (PDR) possibly through the induction of periostin. The purpose of this study was to determine whether macrophage colony-stimulating factor (M-CSF) and interleukin (IL)-13, inducers of the M2 polarisation of macrophages from monocytes, are elevated in the vitreous of patients with PDR, and whether M2-polarised macrophages induce periostin production.

METHODS

We measured the levels of M-CSF, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-4, IL-13, soluble (s)CD163, periostin and vascular endothelial growth factor by sandwich ELISA in vitreous samples collected from 61 eyes of 47 patients with PDR, and 39 eyes of 36 patients with non-diabetic ocular diseases (control group). Human monocytes were polarised in vitro with GM-CSF, interferon-γ, and lipopolysaccharide for M1 macrophages, and M-CSF, IL-4, and IL-13 for M2 macrophages. Quantitative real-time PCR was used to determine the mRNA level of periostin.

RESULTS

The concentrations of M-CSF and IL-13 in the vitreous were significantly higher in patients with PDR than in non-diabetic controls (p<0.0001). There was a strong positive correlation between the vitreous concentrations of M-CSF and sCD163 and periostin. The mean vitreous level of IL-13 was significantly higher in eyes with FVMs than in those without FVMs (epicentre only). In vitro studies showed that M2-polarlised macrophages significantly increased the expression of the mRNA of periostin.

CONCLUSIONS

These findings indicate that the M2 polarisation of macrophages is induced by M-CSF and IL-13 in diabetic retinas. The presence of M-CSF and IL-13 would then promote FVM formation by periostin production.

Overexpression of CD163 in vitreous and fibrovascular membranes of patients with proliferative diabetic retinopathy: possible involvement of periostin

AIM

To determine whether CD163, a specific marker for M2 macrophages, is involved in the formation of preretinal fibrovascular membranes (FVMs) present in eyes with proliferative diabetic retinopathy (PDR).

METHODS

We measured the levels of soluble (s)CD163, periostin and vascular endothelial growth factor by sandwich ELISA in vitreous samples from 74 eyes of 62 patients with PDR, 20 eyes of 18 patients with proliferative vitreoretinopathy, and 56 eyes of 54 patients with non-diabetic ocular diseases (control group). Immunohistochemical analyses were performed to determine the expressions of CD68, CD163 and periostin in the surgically resected FVMs and idiopathic epiretinal membranes (ERMs).

RESULTS

The concentrations of sCD163 and periostin in the vitreous were significantly higher in patients with PDR than in non-diabetic controls (p<0.0001). There was a strong correlation between the vitreous concentrations of sCD163 and periostin. The mean vitreous level of sCD163 was significantly higher in eyes with FVMs than in those without FVMs (epicentre only). The number and percentage of CD163+ macrophages were significantly higher in the FVMs than in the idiopathic ERMs. Immunohistochemical analysis showed co-localisation of CD163 and periostin in FVM cells.

CONCLUSIONS

These findings indicate that the overexpression of CD163 by macrophages may be involved in the development of FVMs partly through periostin production.

Valley-dependent spin polarization in bulk MoS2 with broken inversion symmetry

The valley degree of freedom of electrons is attracting growing interest as a carrier of information in various materials, including graphene, diamond and monolayer transition-metal dichalcogenides. The monolayer transition-metal dichalcogenides are semiconducting and are unique due to the coupling between the spin and valley degrees of freedom originating from the relativistic spin-orbit interaction. Here, we report the direct observation of valley-dependent out-of-plane spin polarization in an archetypal transition-metal dichalcogenide--MoS2--using spin- and angle-resolved photoemission spectroscopy. The result is in fair agreement with a first-principles theoretical prediction. This was made possible by choosing a 3R polytype crystal, which has a non-centrosymmetric structure, rather than the conventional centrosymmetric 2H form. We also confirm robust valley polarization in the 3R form by means of circularly polarized photoluminescence spectroscopy. Non-centrosymmetric transition-metal dichalcogenide crystals may provide a firm basis for the development of magnetic and electric manipulation of spin/valley degrees of freedom.

Hyphema is a risk factor for failure of trabeculectomy in neovascular glaucoma: a retrospective analysis

Background

Several retinal ischemic diseases can cause neovascular glaucoma (NVG). Trabeculectomy with mitomycin C (MMC) is a relatively better treatment modality in the management of eyes with NVG than other glaucoma surgeries. The aim of this study was to investigate the factors that may influence the outcome of trabeculectomy with MMC for NVG.

Methods

Forty-nine NVG eyes from 43 patients (26 males and 17 females) underwent primary trabeculectomy with MMC. The mean follow-up period was 16.8 ± 8.1 months (range, 6 to 34 months). Twenty-one eyes of 21 patients received intravitreal bevacizumab (IVB) 3.6 ± 1.8 days before trabeculectomy with MMC. A Kaplan-Meier survival-curve analysis was used to summarize the cumulative probability of success. We examined the relationship between the surgical outcome and the following surgical factors: gender, age, history of panretinal photocoagulation, history of cataract surgery, history of vitrectomy, preoperative IVB, NVG in the fellow eye, and postoperative complications (hyphema, choroidal detachment, and formation of fibrin) by multivariate analysis.

Results

The survival rate was 83.7% after 6 months, 70.9% after 12 months, and 60.8% after 24 months. The Kaplan-Meier survival curves showed no significant difference in the survival rate between the eyes with preoperative IVB (n = 21) and the eyes without preoperative IVB (n = 28) (p = 0.14). The multiple logistic regression analysis showed that postoperative hyphema (odds ratio, 6.54; 95% confidence interval, 1.41 to 35.97) was significantly associated with the surgical outcome (p = 0.02).

Conclusions

Postoperative hyphema was significantly correlated with the outcome of trabeculectomy for NVG. There was no significant association between preoperative IVB and postoperative hyphema or the results of trabeculectomy.

Periostin promotes the generation of fibrous membranes in proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR) is a severe, vision-threatening disorder characterized by the fibrous membrane formation that leads to tractional retinal detachment. There has been no effective therapeutic approach other than vitreoretinal surgery. In this study, DNA microarray analysis of the fibrous membranes revealed significant up-regulation of periostin. We also found increased periostin expression in the vitreous and retinal pigment epithelial (RPE) cells from fibrous membranes of PVR patients. In vitro, periostin increased proliferation, adhesion, migration, and collagen production in RPE cells through integrin αV-mediated FAK and AKT phosphorylation. Periostin blockade suppressed migration and adhesion induced by TGFβ2 and PVR vitreous. In vivo, periostin inhibition had the inhibitory effect on progression of experimental PVR in rabbit eyes without affecting the viability of retinal cells. These results identified periostin as a pivotal molecule for fibrous membrane formation as well as a promising therapeutic target for PVR.

Wide-field laser ophthalmoscopy for mice: a novel evaluation system for retinal/choroidal angiogenesis in mice

PURPOSE

The purpose of this study was to investigate the application of wide-field laser ophthalmoscopy (Optos) for the evaluation of established models of angiogenesis and the healthy retina in mice.

METHODS

To investigate whether angiogenesis and leakage in the retina and choroid can be evaluated with Optos, we used two models of angiogenesis: oxygen-induced retinopathy (OIR) and laser-induced choroidal neovascularization (CNV). Fundus imaging and fluorescein angiography (FAG) were performed with the Optos system without a contact lens. Furthermore, to evaluate in vivo leukocyte infiltration in these models, we injected acridine orange (AO) and performed imaging using Optos.

RESULTS

In vivo fundus imaging with Optos did not require any additional optical device. Additionally, Optos enabled us to repeatedly obtain high-resolution color images and FAG images in the OIR model as well as in the CNV model in mice. Through a combination of Optos imaging and AO fluorography, the number and location of the infiltrating leukocytes could be identified in these models.

CONCLUSIONS

Optos is a wide-viewing imaging tool for the noninvasive in vivo evaluation of common angiogenesis models, oxygen-induced retinopathy and laser-induced choroidal neovascularization, as well as the healthy retina in mice.

Extremely high electron mobility in a phonon-glass semimetal

The electron mobility is one of the key parameters that characterize the charge-carrier transport properties of materials, as exemplified by the quantum Hall effect as well as high-efficiency thermoelectric and solar energy conversions. For thermoelectric applications, introduction of chemical disorder is an important strategy for reducing the phonon-mediated thermal conduction, but is usually accompanied by mobility degradation. Here, we show a multilayered semimetal β-CuAgSe overcoming such a trade-off between disorder and mobility. The polycrystalline ingot shows a giant positive magnetoresistance and Shubnikov de Haas oscillations, indicative of a high-mobility small electron pocket derived from the Ag s-electron band. Ni doping, which introduces chemical and lattice disorder, further enhances the electron mobility up to 90,000 cm(2) V(-1) s(-1) at 10 K, leading not only to a larger magnetoresistance but also a better thermoelectric figure of merit. This Ag-based layered semimetal with a glassy lattice is a new type of promising thermoelectric material suitable for chemical engineering.

Dependence of carrier doping on the impurity potential in transition-metal-substituted FeAs-based superconductors

In order to examine to what extent the rigid-band-like electron doping scenario is applicable to the transition metal-substituted Fe-based superconductors, we have performed angle-resolved photoemission spectroscopy studies of Ba(Fe(1-x)Ni(x))(2)As(2) (Ni-122) and Ba(Fe(1-x)Cu(x))(2)As(2) (Cu-122), and compared the results with Ba(Fe(1-x)Co(x))(2)As(2) (Co-122). We find that Ni 3d-derived features are formed below the Fe 3d band and that Cu 3d-derived ones further below it. The electron and hole Fermi surface (FS) volumes are found to increase and decrease with substitution, respectively, qualitatively consistent with the rigid-band model. However, the total extra electron number estimated from the FS volumes (the total electron FS volume minus the total hole FS volume) is found to decrease in going from Co-, Ni-, to Cu-122 for a fixed nominal extra electron number, that is, the number of electrons that participate in the formation of FS decreases with increasing impurity potential. We find that the Néel temperature T(N) and the critical temperature T(c) maximum are determined by the FS volumes rather than the nominal extra electron concentration or the substituted atom concentration.

Strongly spin-orbit coupled two-dimensional electron gas emerging near the surface of polar semiconductors

We investigate the two-dimensional highly spin-polarized electron accumulation layers commonly appearing near the surface of n-type polar semiconductors BiTeX (X=I, Br, and Cl) by angular-resolved photoemission spectroscopy. Because of the polarity and the strong spin-orbit interaction built in the bulk atomic configurations, the quantized conduction-band subbands show giant Rashba-type spin splitting. The characteristic 2D confinement effect is clearly observed also in the valence bands down to the binding energy of 4 eV. The X-dependent Rashba spin-orbit coupling is directly estimated from the observed spin-split subbands, which roughly scales with the inverse of the band-gap size in BiTeX.

Enhanced infrared magneto-optical response of the nonmagnetic semiconductor BiTeI driven by bulk Rashba splitting

We study the magneto-optical (MO) response of the polar semiconductor BiTeI with giant bulk Rashba spin splitting at various carrier densities. Despite being nonmagnetic, the material is found to yield a huge MO activity in the infrared region under moderate magnetic fields (up to 3 T). Our first-principles calculations show that the enhanced MO response of BiTeI comes mainly from the intraband transitions between the Rashba-split bulk conduction bands. These transitions connecting electronic states with opposite spin directions become active due to the presence of strong spin-orbit interaction and give rise to distinct features in the MO spectra with a systematic doping dependence. We predict an even more pronounced enhancement in the low-energy MO response and dc Hall effect near the crossing (Dirac) point of the conduction bands.

Mechanisms of enhanced orbital dia- and paramagnetism: application to the Rashba semiconductor BiTeI

We study the magnetic susceptibility of a layered semiconductor BiTeI with giant Rashba spin splitting both theoretically and experimentally to explore its orbital magnetism. Apart from the core contributions, a large temperature-dependent diamagnetic susceptibility is observed when the Fermi energy E(F) is near the crossing point of the Rashba spin-split conduction bands at the time-reversal symmetry point A. On the other hand, when E(F) is below this band crossing, the susceptibility turns to be paramagnetic. These features are consistent with first-principles calculations, which also predict an enhanced orbital magnetic susceptibility with both positive and negative signs as a function of E(F) due to band (anti)crossings. Based on these observations, we propose two mechanisms for the enhanced paramagnetic orbital susceptibility.

Ab initio studies on the interplay between spin-orbit interaction and Coulomb correlation in Sr2IrO4 and Ba2IrO4

Ab initio analyses of A(2)IrO(4) (A=Sr,Ba) are presented. Effective Hubbard-type models for Ir 5d t(2g) manifolds downfolded from the global band structure are solved based on the dynamical mean-field theory. The results for A=Sr and Ba correctly reproduce paramagnetic metals undergoing continuous transitions to insulators below the Néel temperature T(N). These compounds are classified not into Mott insulators but into Slater insulators. However, the insulating gap opens by a synergy of the Néel order and significant band renormalization, which is also manifested by a 2D bad metallic behavior in the paramagnetic phase near the quantum criticality.

Emergence of non-centrosymmetric topological insulating phase in BiTeI under pressure

The spin-orbit interaction affects the electronic structure of solids in various ways. Topological insulators are one example in which the spin-orbit interaction leads the bulk bands to have a non-trivial topology, observable as gapless surface or edge states. Another example is the Rashba effect, which lifts the electron-spin degeneracy as a consequence of the spin-orbit interaction under broken inversion symmetry. It is of particular importance to know how these two effects, that is, the non-trivial topology of electronic states and the Rashba spin splitting, interplay with each other. Here we show through sophisticated first-principles calculations that BiTeI, a giant bulk Rashba semiconductor, turns into a topological insulator under a reasonable pressure. This material is shown to exhibit several unique features, such as a highly pressure-tunable giant Rashba spin splitting, an unusual pressure-induced quantum phase transition, and more importantly, the formation of strikingly different Dirac surface states at opposite sides of the material.

[Mechanism of diabetes-induced microvascular damage and therapeutic potential of ROCK inhibition]

The rapid increase in diabetic retinopathy (DR), a common ocular complication of diabetes mellitus, necessitates the development of new therapeutic strategies for the amelioration and treatment of DR, especially in the earlier stages. In the present study, involvement of the Rho/Rho-kinase (ROCK) pathway in diabetic microvasculopathy and the therapeutic potential of fasudil, a selective ROCK inhibitor, were investigated. Retinal microvascular damage secondary to increased leukocyte adhesion substantially contributes to DR in its early stages. Significant Rho/ ROCK activation was observed in the retinal microvasculature of diabetic rats. The ROCK inhibitor, fasudil, protects the vascular endothelium by inhibit- ing leukocyte adhesion and reducing leukocyte-induced endothelial injury mediated through the restoration of endothelial nitric oxide synthase activity, in the retinas of diabetic rats. In co-culture assay of DR leukocytes and microvascular endothelial cells, we investigated the protective mechanisms of fasudil on endothelial damage using L-NAME, an inhibitor of nitric oxide synthase. Leukocytes from DR patients caused endothelial apoptosis via Fas/ FasL interaction, which was significantly reduced by a ROCK inhibition dependent on nitric oxide. The Rho/ROCK pathway plays a critical role in diabetic retinal microvasculopathy and ROCK inhibition may become a new strategy in the amelioration and treatment of DR, especially in its early stages.

Optical response of relativistic electrons in the polar BiTeI semiconductor

The transitions between the spin-split bands by spin-orbit interaction are relevant to many novel phenomena such as the resonant dynamical magnetoelectric effect and the spin Hall effect. We perform optical spectroscopy measurements combined with first-principles calculations to study these transitions in the recently discovered giant bulk Rashba spin-splitting system BiTeI. Several novel features are observed in the optical spectra of the material including a sharp edge singularity due to the reduced dimensionality of the joint density of states and a systematic doping dependence of the intraband transitions between the Rashba-split branches. These confirm the bulk nature of the Rashba-type splitting in BiTeI and manifest the relativistic nature of the electron dynamics in a solid.

Giant Rashba-type spin splitting in bulk BiTeI

There has been increasing interest in phenomena emerging from relativistic electrons in a solid, which have a potential impact on spintronics and magnetoelectrics. One example is the Rashba effect, which lifts the electron-spin degeneracy as a consequence of spin-orbit interaction under broken inversion symmetry. A high-energy-scale Rashba spin splitting is highly desirable for enhancing the coupling between electron spins and electricity relevant for spintronic functions. Here we describe the finding of a huge spin-orbit interaction effect in a polar semiconductor composed of heavy elements, BiTeI, where the bulk carriers are ruled by large Rashba-like spin splitting. The band splitting and its spin polarization obtained by spin- and angle-resolved photoemission spectroscopy are well in accord with relativistic first-principles calculations, confirming that the spin splitting is indeed derived from bulk atomic configurations. Together with the feasibility of carrier-doping control, the giant-Rashba semiconductor BiTeI possesses excellent potential for application to various spin-dependent electronic functions.

Two-dimensional and three-dimensional Fermi surfaces of superconducting BaFe2(As(1-x)P(x))2 and their nesting properties revealed by angle-resolved photoemission spectroscopy

We have studied the three-dimensional shapes of the Fermi surfaces (FSs) of BaFe(2)(As(1-x)P(x))(2) (x=0.38), where superconductivity is induced by isovalent P substitution and by angle-resolved photoemission spectroscopy. Moderately strong electron mass enhancement has been identified for both the electron and hole FSs. Among two observed hole FSs, the nearly two-dimensional one shows good nesting with the outer two-dimensional electron FS, but its orbital character is different from the outer electron FS. The three-dimensional hole FS shows poor nesting with the electron FSs. The present results suggest that the three dimensionality and the difference in the orbital character weaken FS nesting while partial nesting among the outer electron FSs of d(xy) character and/or that within the three-dimensional hole FS becomes dominant, which may lead to the nodal superconductivity.

Pseudogap of metallic layered nickelate R(2-x)Sr(x)NiO4 (R = Nd, Eu) crystals measured using angle-resolved photoemission spectroscopy

We have investigated charge dynamics and electronic structures for single crystals of metallic layered nickelates, R(2-x)Sr(x)NiO4 (R = Nd, Eu), isostructural to La(2-x)Sr(x)CuO4. Angle-resolved photoemission spectroscopy on the barely metallic Eu(0.9)Sr(1.1)NiO4 (R = Eu, x = 1.1) has revealed a large hole surface of x2-y2 character with a high-energy pseudogap of the same symmetry and comparable magnitude with those of underdoped (x<0.1) cuprates, although the antiferromagnetic interactions are 1 order of magnitude smaller. This finding strongly indicates that the momentum-dependent pseudogap feature in the layered nickelate arises from the real-space charge correlation.

Histopathology of neovascular tissue from eyes with proliferative diabetic retinopathy after intravitreal bevacizumab injection

PURPOSE

To examine the histopathologic effect of a single intravitreal injection of bevacizumab on newly formed vessels in eyes with proliferative diabetic retinopathy (PDR).

DESIGN

Interventional case series and laboratory investigation.

METHODS

Two days after intravitreal injection of bevacizumab (1.25 mg/eye), pars plana vitrectomy or trabeculectomy was performed for the treatment of PDR or neovascular glaucoma (NVG) associated with PDR. Ten surgically removed preretinal proliferative tissues and 6 deep scleral flaps containing trabecular meshwork were fixed in 2% glutaraldehyde or 4% paraformaldehyde and were subjected to transmission electron microscopic analysis, immunohistochemical analysis, and terminal deoxyuridiine triphosphate (dUTP) nick-end labeling staining. Two surgically removed preretinal proliferative tissues and 2 deep scleral flaps from patients with PDR and NVG, but without preoperative intravitreal injection of bevacizumab (IVB), served as controls.

RESULTS

In control tissues, vascular endothelial cells possessed many fenestrations and were accompanied by pericytes. Apoptotic vascular endothelial cells frequently were observed in tissue after intravitreal injection of bevacizumab, whereas they were not observed in control tissues. Additionally, no apparent fenestration was observed in newly formed vessels from either proliferative tissue or trabecular meshwork after intravitreal injection of bevacizumab. In both PDR and NVG tissues after intravitreal injection of bevacizumab, overexpression of smooth muscle actin was observed in newly formed vessels, suggesting that the treatment may have increased pericytes on the vasculature as compared with control tissue.

CONCLUSIONS

Intravitreal injection of bevacizumab may induce changes in immature, newly formed vessels of PDR or NVG tissue, leading to endothelial apoptosis with vascular regression, while inducing normalization of premature vessels by increasing pericyte coverage and reducing vessel fenestration.

Dichotomy between large local and small ordered magnetic moments in iron-based superconductors

We study a four-band model for iron-based superconductors within the local density approximation combined with dynamical mean-field theory (LDA+DMFT). This successfully reproduces the results of models which take As p degrees of freedom explicitly into account and has several physical advantages over the standard five d-band model. Our findings reveal that the new superconductors are more strongly correlated than their single-particle properties suggest. Two-particle correlation functions unveil the dichotomy between local and ordered magnetic moments in these systems, calling for further experiments to better resolve the short time scale spin dynamics.

Antiangiogenic mechanisms of simvastatin in retinal endothelial cells

BACKGROUND

While statins have an anti-angiogenic property, their underlying mechanisms are not fully understood. We investigated intracellular mechanisms of simvastatin-mediated reduction in VEGF-induced signalings.

METHODS

The effects of simvastatin on cell proliferation and viability were evaluated by [(3)H]-thymidine incorporation in retinal endothelial cells (RECs) and cell counting. The impact of simvastatin on VEGF-induced phosphorylation of p44/42 mitogen-activated protein (MAP) kinase, myosin light chain (MLC), and VEGF-receptor (VEGFR) 2 were examined by Western blotting. Involvement of the mevalonate pathway in VEGF-induced signaling was also examined.

RESULTS

Simvastatin (1 and 10 microM) suppressed VEGF-induced RECs proliferation in a concentration-dependent manner, without affecting cell viability. Simvastatin significantly inhibited VEGF-induced phosphorylation of VEGFR2 and its downstream mediators, p44/42 MAP kinase and MLC. Mevalonate completely reversed VEGF-induced VEGFR2 phosphorylation, but only partially reversed the phosphorylation of p44/42 MAP kinase and MLC.

CONCLUSION

These data indicate that simvastatin exerts its anti-angiogenic effects through the reduction of VEGFR2 phosphorylation in RECs at least in part. However, there seems to be both mevalonate-dependent and independent pathway in simvastatin's anti-angiogenic property.

Equivalent tamponade by room air as compared with SF(6) after macular hole surgery

BACKGROUND

To evaluate the effect of tamponade by room air after vitrectomy for the treatment of idiopathic macular hole (MH).

METHODS

There were 156 eyes of 151 patients studied. The patients' ages ranged from 35 to 88 years old (mean: 65.1 years). After conventional pars plana vitrectomy with internal limiting membrane peeling, fluid air exchange was performed using 20% SF(6) (Gas group: 91 eyes) or room air (Air group: 65 eyes). Surgical outcomes were retrospectively analyzed.

RESULTS

Mean preoperative hole diameter was 352 microm in the Gas group and 370 microm in the Air group (P = 0.558). The closure rate of all cases was 91.0% after first surgery and 98.7% at last follow-up. The primary closure rate was 90.1% in the Gas group after 7.44 +/- 1.66 (mean +/- SD) days prone positioning period, and 92.3% in the Air group after 3.83 +/- 0.97 days of prone positioning. There was significant difference in prone positioning period (P < 0.0001), but not in the first closure rate (P = 0.132).

CONCLUSION

This study suggests that room air may have an equivalent tamponade effect, in spite of the shorter prone positioning period, than SF(6) after MH surgery.