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In this work, we use the liquid ammonia method to successfully intercalate potassium atoms into ZrTe5 single crystal, and find a transition from semimetal to semiconductor at low temperature in the intercalated ZrTe5. The resistance anomalous peak is gradually suppressed and finally disappears with increasing potassium concentration. Whilst, the according sign reversal is always observed in the Hall resistance measurement. We tentatively attribute the semimetal-semiconductor transition to the lattice expansion induced by atomic intercalation and thereby a larger energy band gap., 16 pages, 5 figures

In the electronic nematic state, an electronic system has a lower symmetry than the crystal structure of the same system. Electronic nematic states have been observed in various unconventional superconductors such as cuprate, iron-based, heavy-fermion, and topological superconductors. The relation between nematicity and superconductivity is a major unsolved problem in condensed matter physics. By angle-resolved specific heat measurements, we report bulk quasiparticle evidence of nematicity in the topological superconductor Sr_{x}Bi_{2}Se_{3}. The specific heat exhibited a clear twofold symmetry despite the threefold symmetric lattice. Most importantly, the twofold symmetry appeared in the normal state above the superconducting transition temperature. This is explained by the angle-dependent Zeeman effect due to the anisotropic density of states in the nematic phase. Such results highlight the interrelation between nematicity and unconventional superconductivity.

The study of transverse resistance of superconductors is essential to understand the transition to superconductivity. Here, we investigated the in-plane transverse resistance of Ba0.5K0.5Fe2As2 superconductors, based on ultra-thin micro-bridges fabricated from optimally doped single crystals. An anomalous transverse resistance was found at temperatures around the superconducting transition, although magnetic order or structure distortion are absent in the optimal doping case. With the substitution of magnetic and nonmagnetic impurities into the superconducting layer, the anomalous transverse resistance phenomenon is dramatically enhanced. We find that anisotropic scattering or the superconducting electronic nematic state related with the superconducting transition may contribute to this phenomenon.

To realize topological superconductor is one of the most attracting topics because of its great potential in quantum computation. In this study, we successfully intercalate potassium (K) into the van der Waals gap of type II Weyl semimetal WTe2, and discover the superconducting state in KxWTe2 through both electrical transport and scanning tunneling spectroscopy measurements. The superconductivity exhibits an evident anisotropic behavior. Moreover, we also uncover the coexistence of superconductivity and the positive magneto-resistance state. Structural analysis substantiates the negligible lattice expansion induced by the intercalation, therefore suggesting K-intercalated WTe2 still hosts the topological nontrivial state. These results indicate that the K-intercalated WTe2 may be a promising candidate to explore the topological superconductor., Comment: 17 pages, 4 figures

We report protonation in several compounds by an ionic-liquid-gating method, with optimized gating conditions. This leads to single superconducting phases for several compounds. Non-volatility of protons allow post-gating magnetization and transport measurements. The superconducting transition temperature $T_C$ is enhanced to 43.5~K for FeSe$_{0.93}$S$_{0.07}$, and 41~K for FeSe after protonation. Superconductivity with $T_c$$\approx$15~K for ZrNCl, $\approx$7.2~K for 1$T$-TaS$_2$, and $\approx$3.8~K for Bi$_2$Se$_3$ are induced after protonation. Electric transport in protonated FeSe$_{0.93}$S$_{0.07}$ confirms high-temperature superconductivity. Our $^{1}$H NMR measurements on protonated FeSe$_{1-x}$S$_{x}$ reveal enhanced spin-lattice relaxation rate $1/^{1}T_1$ with increasing $x$, which is consistent with LDA calculations that H$^{+}$ are located in the interstitial sites close to the anions., Comment: 4 pages, 7 figures

Superconductivity mediated by phonons is typically conventional, exhibiting a momentum-independent s-wave pairing function, due to the isotropic interactions between electrons and phonons along different crystalline directions. Here, by performing inelastic neutron scattering measurements on a superconducting single crystal of Sr0.1Bi2Se3, a prime candidate for realizing topological superconductivity by doping the topological insulator Bi2Se3, we find that there exist highly anisotropic phonons, with the linewidths of the acoustic phonons increasing substantially at long wavelengths, but only for those along the [001] direction. This observation indicates a large and singular electron-phonon coupling at small momenta, which we propose to give rise to the exotic p-wave nematic superconducting pairing in the MxBi2Se3 (M = Cu, Sr, Nb) superconductor family. Therefore, we show these superconductors to be example systems where electron-phonon interaction can induce more exotic superconducting pairing than the s-wave, consistent with the topological superconductivity., Superconductivity mediated by phonons is usually conventional due to isotropic electron-phonon coupling. Here, Wang et al. report highly anisotropic phonons only along [001] direction in Sr0.1Bi2Se3, indicating a singular electron-phonon coupling which favors a p-wave nematic superconductivity scenario.

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

Using a machine-learning accelerated crystal structural search, and ab initio calculations together with high-pressure Raman measurements, we study the crystal and electronic structures of bismuth iodide (BiI) systematically up to 50 GPa. We find that the ambient $C2/m$ phase ($\ensuremath{\beta}\ensuremath{-}\mathrm{B}{\mathrm{i}}_{4}{\mathrm{I}}_{4}$) transforms across a tetragonal $P{4}_{2}/mmc$ phase at 8.5 GPa and finally to a hexagonal $P{6}_{3}/mmc$ phase at 28.2 GPa. Our high-pressure Raman experiments identify a phase transition at around 8.6 GPa, and the experimental Raman modes evolution agrees with our calculations reasonably. Band-structures calculations suggest the BiI system undergoes a pressure-induced topological phase transition from a topological metal ($P{4}_{2}/mmc$ phase) to a trivial metal (the $P{6}_{3}/mmc$ phase). Our electron-phonon coupling calculations show both the $P{4}_{2}/mmc$ and $P{6}_{3}/mmc$ phases are superconductors and the estimated superconducting critical temperature agrees with previous measurements. Our study shows the previously reported pressure-induced superconductivity in BiI should originate from structure phase transitions.

MPT63 protein is found only in Mycobacterium tuberculosis complex, including M. tuberculosis and M. bovis. Detection of MPT63-specific IFN-γ-secreting T cells could be useful for the diagnosis of tuberculosis (TB) diseases. In the present study, the HLA-A*0201 restriction of ten predicted MPT63-derived CD8(+) T-cell epitopes was assessed on the basis of T2 cell line and HLA-A*0201 transgenic mice. The diagnostic potential of immunogenic peptides in active pulmonary TB patients was evaluated using an IFN-γ enzyme-linked immunospot assay. It was found that five peptides bound to HLA-A*0201 with high affinity, whereas the remaining peptides exhibited low affinity for HLA-A*0201. Five immunogenic peptides (MPT6318-26 , MPT6329-37 , MPT6320-28 , MPT635-14 and MPT6310-19 ) elicited large numbers of cytotoxic IFN-γ-secreting T cells in HLA-A*0201 transgenic mice. Each of the five immunogenic peptides was recognized by peripheral blood mononuclear cells from 45% to 73% of 40 HLA-A*0201 positive TB patients. The total diagnostic sensitivity of the five immunogenic peptides was higher than that of a T-SPOT.TB assay (based on ESAT-6 and CFP-10) (93% versus 90%). It is noticeable that the diagnostic sensitivity of the combination of five immunogenic peptides and T-SPOT.TB assay reached 100%. These MPT63-derived HLA-A*0201-restricted CD8(+) T-cell epitopes would likely contribute to the immunological diagnosis of M. tuberculosis infection and may provide the components for designing an effective TB vaccine.

Dengue virus (DENV) and Zika virus (ZIKV) are antigenically related mosquito-transmitted viruses which represent a big public health problem. Although the antigenic cross-reactivity between two viruses were intensively investigated at the antibody and T cell levels, how DENV envelope protein domain III (EDIII)-elicited antibodies (Abs) impact the outcome of ZIKV infection is uncertain. Here, our results show that the sera isolated from DENV-EDIII-immunized wild-type mice recognized ZIKV-EDIII and cross-neutralized ZIKV in vitro. Passive transfer of DENV-EDIII-immune sera protected 1-day-old mice against lethal ZIKV challenge. Finally, maternally acquired anti-DENV-EDIII Abs significantly increased the survival of 1-day-old mice born to DENV-EDIII-immunized mothers post ZIKV challenge. These results reveal that DENV-EDIII-induced Abs provide cross-protection against ZIKV and may not mediate the Ab-dependent enhancement of ZIKV infection at the concentration used here. The present study would contribute to the development and application of DENV-EDIII-based vaccines.

Gallium, aluminum, and indium belong to Group IIIA of the periodic table with similar chemical properties, which were a double-edged sword for living organisms. Therefore, it's particularly important to detect the content of Group IIIA in organisms. Obviously, the fluorescent probe method has become a mainstream method for detecting metal ions with advantages of convenience and high efficiency. Unfortunately, fluorescent probes that can simultaneously detect these three metal ions are rarely reported. 3-hydroxyflavone (3-HF) is a highly focused molecule with chemical and photochemical properties and have great potential for bioimaging applications as sensors with excited-state intramolecular proton transfer (ESIPT). Here, 3-HF as ratiometric fluorescence probes have been developed for responding to Group IIIA ions including Ga(III), Al(III) and In(III) ions with ESIPT-based mechanism. 3-HF displayed highly specific sensing for Group IIIA ions over other cations with a green fluorescence transformation into blue fluorescence by the formation of 2:1 complexes. However, rapid response toward Group IIIA ions was developed using ratiometric fluorescence with wide pH range and good reversibility, and the response mechanism of 3-HF toward Group IIIA ions was annotated by density functional theory (DFT). Furthermore, the biological applicability of 3-HF has shown that 3-HF were able to detect and image Group IIIA ions in cells. Additionally, using a zebrafish model, we exhibited the capability of this 3-HF probe for detecting and imaging Group IIIA ions in zebrafish. This work achieves the detection and imaging of Group IIIA simultaneously by 3-HF probe in living cells and zebrafish and provides another example for “ESIPT OFF”.

SUMMARY The underlying mechanisms by which prior immunity to dengue virus (DENV) affords cross-protection against the related flavivirus Zika virus (ZIKV) are poorly understood. Here, we examine the ability of DENV/ZIKV-cross-reactive CD4+ T cells to protect against versus exacerbate ZIKV infection by using a histocompatibility leukocyte antigen (HLA)-DRB1*0101 transgenic, interferon α/β receptor-deficient mouse model that supports robust DENV and ZIKV replication. By mapping the HLA-DRB1*0101-restricted T cell response, we identify DENV/ZIKV-cross-reactive CD4+ T cell epitopes that stimulate interferon gamma (IFNγ) and/or tumor necrosis factor (TNF) production. Vaccination of naive HLA-DRB1*0101 transgenic mice with these peptides induces a CD4+ T cell response sufficient to reduce tissue viral burden following ZIKV infection. Notably, this protective response requires IFNγ and/or TNF secretion but not anti-ZIKV immunoglobulin G (IgG) production. Thus, DENV/ZIKV-cross-reactive CD4+ T cells producing canonical Th1 cytokines can suppress ZIKV replication in an antibody-independent manner. These results may have important implications for increasing the efficacy and safety of DENV/ZIKV vaccines and for developing pan-flavivirus vaccines., Graphical Abstract, In Brief Wen et al. show that dengue and Zika virus cross-reactive CD4+ T cells reduce Zika viral burden in interferon α/β receptor-deficient HLA-DRB1*0101 transgenic mice in an IFNγ- or TNF-dependent, antibody-independent manner.

To realize a topological superconductor is one of the most attracting topics because of its great potential in quantum computation. In this study, we successfully intercalate potassium (K) into the van der Waals gap of type II Weyl semimetal WTe

We present inelastic neutron scattering results of phonons in ${({\mathrm{Pb}}_{0.5}{\mathrm{Sn}}_{0.5})}_{1\ensuremath{-}x}{\mathrm{In}}_{x}\mathrm{Te}$ powders, with $x=0$ and 0.3. The $x=0$ sample is a topological crystalline insulator, and the $x=0.3$ sample is a superconductor with a bulk superconducting transition temperature ${T}_{c}$ of 4.7 K. In both samples, we observe unexpected van Hove singularities in the phonon density of states at energies of 1--2.5 meV, suggestive of local modes. On cooling the superconducting sample through ${T}_{c}$, there is an enhancement of these features for energies below twice the superconducting-gap energy. We further note that the superconductivity in ${({\mathrm{Pb}}_{0.5}{\mathrm{Sn}}_{0.5})}_{1\ensuremath{-}x}{\mathrm{In}}_{x}\mathrm{Te}$ occurs in samples with normal-state resistivities of order 10 $\mathrm{m}\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\mathrm{cm}$, indicative of bad-metal behavior. Calculations based on density functional theory suggest that the superconductivity is easily explainable in terms of electron-phonon coupling; however, they completely miss the low-frequency modes and do not explain the large resistivity. While the bulk superconducting state of ${({\mathrm{Pb}}_{0.5}{\mathrm{Sn}}_{0.5})}_{0.7}{\mathrm{In}}_{0.3}\mathrm{Te}$ appears to be driven by phonons, a proper understanding will require ideas beyond simple BCS theory.

Recently, there have been increasingly hot debates on whether there exists a quantum spin liquid in the Kitaev honeycomb magnet α-RuCl_{3} in a high magnetic field. To investigate this issue, we perform ultralow-temperature thermal conductivity measurements on single crystals of α-RuCl_{3} down to 80 mK and up to 9 T. Our experiments clearly show a field-induced phase transition occurring at μ_{0}H_{c}≈7.5 T, above which the magnetic order is completely suppressed. The minimum of thermal conductivity at 7.5 T is attributed to the strong scattering of phonons by magnetic fluctuations. Most importantly, above 7.5 T, we do not observe any significant contribution of thermal conductivity from gapless magnetic excitations, which puts a strong constraint on the nature of the high-field phase of α-RuCl_{3}.

Objective To identify Mycobacterium tuberculosis ESAT-6 protein esxN-specific HLA-A*0201-restricted CTL epitopes and assess the diagnostic potential of the identified epitopes in pulmonary tuberculosis. Methods The esxN-specific HLA-A*0201-restricted CTL epitopes were predicted by the T epitope prediction software SYFPEITHI and further synthesized. The binding affinity of the candidate epitopes for HLA-A*0201 was detected using MHC-peptide complex stabilization assay. The immunogenicity of candidate epitopes were assessed using ELISPOT in HLA-A*0201 transgenic mice. Based on identified CTL epitopes, ESAT-6 and culture filtrate protein-10 (CFP-10), the ELISPOT was performed to detect the frequency of epitope/protein-specific CTL. Results In six CTL epitope candidates we tested, two epitopes, esxN

$\alpha$-RuCl$_3$ is a Mott insulator with a honeycomb lattice with strong spin-orbit coupling. We report dielectric measurements on $\alpha$-RuCl$_3$ single crystals under field. At zero field, the dielectric constant, $\epsilon$, drops rapidly when cooled through the magnetic transition temperature T$_N$. With increasing field, the onset of the drop in $\epsilon$ tracks the T$_N$. Such behavior is absent with field above a critical value H$_c$ ~ 7.5 T, indicating the onset of a quantum phase transition. Our data suggest that the dielectric constant can be used as a probe of magnetic ordering in $\alpha$-RuCl$_3$, and $\alpha$-RuCl$_3$ is a possible type-II multiferroics.

$\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$ is a leading candidate material for the observation of physics related to the Kitaev quantum spin liquid (QSL). By combined susceptibility, specific-heat, and nuclear-magnetic-resonance measurements, we demonstrate that $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$ undergoes a quantum phase transition to a QSL in a magnetic field of 7.5 T applied in the $ab$ plane. We show further that this high-field QSL phase has gapless spin excitations over a field range up to 16 T. This highly unconventional result, unknown in either Heisenberg or Kitaev magnets, offers insight essential to establishing the physics of $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$.

We report high-pressure magnetization and $^{35}\mathrm{Cl}$ NMR studies on $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$ with pressure up to 1.5 GPa. At low pressures, the magnetic ordering is identified by both the magnetization data and the NMR data, where the ${T}_{N}$ shows a concave shape dependence with pressure. These data suggest stacking rearrangement along the $c$ axis. With increasing pressure, phase separation appears prominently at $P\ensuremath{\ge}$ 0.45 GPa, and the magnetic volume fraction is completely suppressed at $P\ensuremath{\ge}$ 1.05 GPa. Meanwhile, a phase-transition-like behavior emerges at high pressures in the remaining volume by a sharp drop of magnetization $M(T)$ upon cooling, with the transition temperature ${T}_{x}$ increased to 250 K at 1 GPa. The $1{/}^{35}{T}_{1}$ is reduced by over three orders of magnitude when cooled below 100 K. This characterizes a high-pressure, low-temperature phase with nearly absent static susceptibility and low-energy spin fluctuations. The nature of the high-pressure ground state is discussed, where a magnetically disordered state is proposed as a candidate state.

The 2015-2016 Zika virus (ZIKV) outbreak in the Americas has brought this relatively unknown flavivirus into the spotlight as the etiologic agent of congenital Zika syndrome in newborns and, potentially, of Guillain-Barre syndrome in adults. ZIKV shares a high degree of amino acid sequence homology with the closely related flavivirus Dengue virus (DENV). Due to the paucity of research investigating T cell-mediated immune responses to ZIKV, the precise roles of T cells in protection against and pathogenesis of ZIKV infection are unclear. Nevertheless, knowledge gained from studies of T cell responses to other flaviviruses, such as the four DENV serotypes, provides a framework for investigating and understanding anti-ZIKV T cell responses. In this review, we summarize our current understanding of how T cells respond to primary and secondary infections with DENV and ZIKV. A thorough understanding of the role of ZIKV-specific and DENV cross-reactive T cells in controlling infection is essential for developing ZIKV- and DENV-specific vaccines with maximal safety and efficacy.

I present a brief overview on the interplay between magnetism and superconductivity in one of the Fe-based superconductor systems, Fe 1 + y Te 1 − x Se x , where the research of our group has centered. The parent compound Fe 1 + y Te is an antiferromagnet; with Se doping, antiferromagnetic order is suppressed, followed by the appearance of superconductivity; optimal superconductivity is achieved when x ∼ 50 % , with a superconducting temperature T c of ∼ 15 K. The parent compound has an in-plane magnetic ordering wave vector around (0.5, 0) (using the tetragonal notation with two Fe atoms per cell). When Se concentration increases, the spectral weight appears to be shifted to the wave vector around (0.5, 0.5), accompanying the optimization of superconductivity. A neutron-spin resonance has been observed around (0.5, 0.5) below T c , and is suppressed, along with superconductivity, by an external magnetic field. Taking these evidences into account, it is concluded that magnetism and superconductivity in this system couple to each other closely—while the static magnetic order around (0.5, 0) competes with superconductivity, the spin excitations around (0.5, 0.5) may be an important ingredient for it. I will also discuss the nature of magnetism and substitution effects of 3 d transition metals.

Dengue virus (DENV) has a serious and growing impact on global health and the exact role of DENV-specific CD8(+) T-cells in DENV infection is still uncertain. In the present study, SYFPEITHI algorithm was used to screen the amino acid sequence of Dengue virus serotype 1 (DENV-1) for potential epitopes, and seven putative HLA-A*1101-restricted and five putative HLA-A*2402-restricted epitopes conserved in hundreds of DENV-1 strains were synthesized. The binding affinity of these epitope candidates to corresponding HLA molecules was evaluated using competitive peptide-binding assay. The immunogenicity and specificity of peptides were further tested in HLA-A*1101 transgenic mice, HLA-A*2402 transgenic mice and peripheral blood mononuclear cells (PBMCs) of patients infected with DENV-1. Percentage inhibition (PI) values calculated in competitive peptide-binding assay showed that six peptides (E39-47 PTLDIELLK, NS5(505-513) GVEGEGLHK, NS2b(15-23) SILLSSLLK, NS5(561-569) ALLATSIFK, NS3(99-107) AVEPGKNPK, and NS4b(159-167) VVYDAKFEK) could bind to HLA-A*1101 molecule with high affinity and five peptides (NS3472-480 QYIYMGQPL, NS4a40-48 AYRHAMEEL, NS5(880-888) DYMTSMKRF, NS3(548-556) SYKVASEGF, and NS3(22-30) IYRILQRGL) have a high affinity for HLA-A*2402 molecule. Enzyme-linked immunospot (ELISPOT) results indicated that these high-affinity peptides were recognized by splenocytes of DENV-1-infected transgenic mice and high-affinity peptide-immunized transgenic mice displayed high levels of peptide-specific IFN-γ-secreting cells. In addition, both peptide-pulsed splenocytes and DENV-1-infected splenic monocytes were efficiently killed by these peptide-specific cytotoxic T lymphocytes. Finally, except NS2b(15-23), 10 high-affinity peptides were recognized by PBMCs of patients infected with DENV-1. These identified epitopes would contribute to the understanding of the function of DENV-specific CD8(+) T-cells.

PPE68 is a Mycobacterium tuberculosis-specific protein which is absent from the vaccine strains of BCG. A panel of 14 PPE68-derived peptides predicted to bind to HLA-A*0201 was synthesized. The HLA-A*0201 restriction of these peptides was determined in T2 cell line and HLA-A*0201 transgenic mice. The specificity of peptides was assessed in pulmonary tuberculosis (TB) patients using IFN-γ enzyme-linked immunospot (ELISPOT) assay, and immunodominant peptides were further used to evaluate their diagnostic potential in HLA-A*0201-positive pulmonary TB patients. 13 out of 14 peptides were identified as high-affinity binders. Of these peptides, 12 peptides induced significant IFN-γ-secreting T cell response in transgenic mice and 9 peptides were efficiently recognized by peripheral blood mononuclear cells of 10 HLA-A*0201-positive TB patients. Four immunodominant HLA-A*0201-restricted epitopes (PPE68126-134, PPE68133-141, PPE68140-148, and PPE68148-156) were recognized by the most of 80 HLA-A*0201-positive TB patients (81, 86, 74, and 84 %, respectively). These epitopes may be used for a potential diagnosis of M. tuberculosis infection.

We revisit the phase diagram of the relaxor ferroelectric PMN-xPT using neutron powder diffraction to test suggestions that residual oxygen vacancies and/or strain affect the ground state crystal structure. Powdered samples of PMN-xPT were prepared with nominal compositions of x=0.10, 0.20, 0.30, and 0.40 and divided into two identical sets, one of which was annealed in air to relieve grinding-induced strain and to promote an ideal oxygen stoichiometry. For a given composition and temperature the same structural phase is observed for each specimen. However, the distortions in all of the annealed samples are smaller than those in the as-prepared samples. Further, the diffraction patterns for x=0.10, 0.20, and 0.30 are best refined using the monoclinic Cm space group. By comparing our neutron diffraction results to those obtained on single crystals having similar compositions, we conclude that the relaxor skin effect in PMN-xPT vanishes on the Ti-rich side of the morphotropic phase boundary.

In this study, we set out to identify dengue virus serotype 2 (DENV-2)-specific HLA-A*2402-restricted epitopes and determine the characteristics of T cells generated to these epitopes. We screened the full-length amino-acid sequence of DENV-2 to find potential epitopes using the SYFPEITHI algorithm. Twelve putative HLA-A*2402-binding peptides conserved in hundreds of DENV-2 strains were synthesized, and the HLA restriction of peptides was tested in HLA-A*2402 transgenic mice. Nine peptides (NS4b(228-237), NS2a(73-81), E(298-306), M(141-149), NS4a(96-105), NS4b(159-168), NS5(475-484), NS1(162-171), and NS5(611-620)) induced high levels of peptide-specific IFN-γ-secreting cells in HLA-A*2402 transgenic mice. Apart from IFN-γ, NS4b(228-237-), NS2a(73-81-) and E(298-306)-specific CD8(+) cells produced TNF-α and IL-6 simultaneously, whereas M(141-149-) and NS5(475-484-) CD8(+) cells produced only IL-6. Moreover, splenic mononuclear cells (SMCs) efficiently recognized and killed peptide-pulsed splenocytes. Furthermore, each of nine peptides could be recognized by splenocytes from DENV-2-infected HLA-A*2402 transgenic mice. The SMCs from HLA-A*2402 transgenic mice immunized with nine immunogenic peptides efficiently killed DENV-2-infected splenic monocytes. The present identified epitopes have the potential to be new diagnostic tools for characterization of T-cell immunity in DENV infection and may serve as part of a universal epitope-based vaccine.

Macrophages play a critical role in the host immune response against mycobacterial infection. Our previous study has demonstrated that microRNA-155 (miR-155), one of the most important small non-coding RNAs in the immune system, promotes oxygen-independent mycobacterial killing in macrophages. However, little is known regarding the role of miR-155 in modulating oxygen-dependent mycobactericidal response in macrophages, including the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS). In the present study, we demonstrated that miR-155 was increased in macrophages after Mycobacterium bovis bacille Calmette-Guérin (BCG) infection. Moreover, the BCG-induced upregulation of miR-155 in macrophages was dependent on TLR2, NF-κB and JNK signaling pathways. More importantly, our study explored that miR-155 significantly elevated ROS production in macrophages, although miR-155 had no influence on the inducible nitric oxide synthase (iNOS) expression or nitric oxide (NO) production. In addition, our study demonstrated that miR-155 repressed the expression of src homology 2 (SH2) containing inositol 5-phosphatase1 (SHIP1), and knockdown of SHIP1 greatly increased ROS production in BCG-infected macrophages. Collectively, these data indicate that miR-155 modulates ROS but not RNS production by targeting SHIP1, which may provide a better understanding of the host anti-mycobacterial response.

We report inelastic neutron scattering measurements of low-energy ($\ensuremath{\hbar}\ensuremath{\omega}\ensuremath{\lesssim}10$ meV) magnetic excitations in the ``11'' system ${\mathrm{Fe}}_{1+y}{\mathrm{Te}}_{1\ensuremath{-}x}{\mathrm{Se}}_{x}$. The spin correlations are two-dimensional (2D) in the superconducting samples at low temperature, but appear much more three-dimensional (3D) when the temperature rises well above ${T}_{c}\ensuremath{\sim}15$ K, with a clear increase of the (dynamic) spin correlation length perpendicular to the Fe planes. This behavior is extremely unusual; typically, the suppression of thermal fluctuations at low temperature would favor the enhancement of 3D correlations, or even ordering, and the reversion to 2D cannot be naturally explained when only the spin degree of freedom is considered. Our results suggest that the low temperature physics in the 11 system, in particular the evolution of low-energy spin excitations towards superconducting pairing, intrinsically involves changes in orbital correlations.

Author(s): Li, S; Gan, Y; Wang, J; Zhong, R; Schneeloch, JA; Xu, Z; Tian, W; Stone, MB; Chi, S; Matsuda, M; Sidis, Y; Bourges, P; Li, Q; Gu, G; Tranquada, JM; Xu, G; Birgeneau, RJ; Wen, J | Abstract: We have combined elastic and inelastic neutron scattering techniques, magnetic susceptibility, and resistivity measurements to study single-crystal samples of KxFe2-ySe2, which contain the superconducting phase that has a transition temperature of ∼31 K. In the inelastic neutron scattering measurements, we observe both the spin-wave excitations resulting from the block antiferromagnetic ordered phase and the resonance that is associated with the superconductivity in the superconducting phase, demonstrating the coexistence of these two orders. From the temperature dependence of the intensity of the magnetic Bragg peaks, we find that well before entering the superconducting state, the development of the magnetic order is interrupted, at ∼42 K. We consider this result to be evidence for the physical separation of the antiferromagnetic and superconducting phases; the suppression is possibly due to the proximity effect of the superconducting fluctuations on the antiferromagnetic order.

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

An unexpected superconductivity enhancement is reported in decompressed In2Se3. The onset of superconductivity in In2Se3 occurs at 41.3 GPa with a critical temperature (Tc) of 3.7 K, peaking at 47.1 GPa. The striking observation shows that this layered chalcogenide remains superconducting in decompression down to 10.7 GPa. More surprisingly, the highest Tc that occurs at lower decompression pressures is 8.2 K, a twofold increase in the same crystal structure as in compression. It is found that the evolution of Tc is driven by the pressure-induced R-3m to I-43d structural transition and significant softening of phonons and gentle variation of carrier concentration combined in the pressure quench. The novel decompression-induced superconductivity enhancement implies that it is possible to maintain pressure-induced superconductivity at lower or even ambient pressures with better superconducting performance.

We have grown nearly freestanding single-layer $1{T}^{\ensuremath{'}}\ensuremath{-}\mathrm{WT}{\mathrm{e}}_{2}$ on graphitized $6H$-SiC(0001) by using molecular beam epitaxy (MBE), and characterized its electronic structure with scanning tunneling microscopy/spectroscopy (STM/STS). The existence of topological edge states at the periphery of single-layer $\mathrm{WT}{\mathrm{e}}_{2}$ islands was confirmed. Surprisingly, a bulk band gap at the Fermi level and insulating behaviors were also found in single-layer $\mathrm{WT}{\mathrm{e}}_{2}$ at low temperature, which are likely associated with an incommensurate charge order transition. The realization of two-dimensional topological insulators (2D TIs) in single-layer transition-metal dichalcogenide provides a promising platform for further exploration of the 2D TIs' physics and related applications.

Triggering receptor expressed on myeloid cells 1 (TREM-1) is a receptor mainly expressed on myeloid cells, and it plays an important role in modulating immune response against infectious agents. The function of TREM-1 on nonmyeloid cells such as Vδ2 T cells has not been characterized, and their role in pulmonary tuberculosis (TB) remains unclear. To assess the expression of TREM-1 on blood Vδ2 T cells from pulmonary TB patients and investigate its mechanism of induction, we exploited flow cytometry analysis to study the expression of TREM-1 on Vδ2 T cells from active pulmonary TB patients and control subjects. In this study we demonstrate that TREM-1 (TREM-1

Although dengue virus (DENV) antibodies can neutralize or enhance Zika virus (ZIKV) infection in vitro, their contribution to ZIKV infection in vivo remains unclear. In a recent issue of Science, Bardina et al. (2017) explore the protective versus pathogenic roles of DENV-immune antibodies in ZIKV infection using a mouse model.

An unexpected superconductivity enhancement is reported in decompressed In

α-RuCl_{3} is a leading candidate material for the observation of physics related to the Kitaev quantum spin liquid (QSL). By combined susceptibility, specific-heat, and nuclear-magnetic-resonance measurements, we demonstrate that α-RuCl_{3} undergoes a quantum phase transition to a QSL in a magnetic field of 7.5 T applied in the ab plane. We show further that this high-field QSL phase has gapless spin excitations over a field range up to 16 T. This highly unconventional result, unknown in either Heisenberg or Kitaev magnets, offers insight essential to establishing the physics of α-RuCl_{3}.

CD8+ T cells play an important role in controlling Flavivirus infection, including Zika virus (ZIKV). Here, we have identified 25 HLA-B*0702-restricted epitopes and 1 HLA-A*0101-restricted epitope using interferon (IFN)-γ enzyme-linked immunospot (ELISPOT) and intracellular cytokine staining (ICS) in ZIKV-infected IFN-α/β receptor-deficient HLA transgenic mice. The cross-reactivity of ZIKV epitopes to dengue virus (DENV) was tested using IFN-γ-ELISPOT and IFN-γ-ICS on CD8+ T cells from DENV-infected mice, and five cross-reactive HLA-B*0702-binding peptides were identified by both assays. ZIKV/DENV cross-reactive CD8+ T cells in DENV-immune mice expanded post ZIKV challenge and dominated in the subsequent CD8+ T cell response. ZIKV challenge following immunization of mice with ZIKV-specific and ZIKV/DENV cross-reactive epitopes elicited CD8+ T cell responses that reduced infectious ZIKV levels, and CD8+ T cell depletions confirmed that CD8+ T cells mediated this protection. These results identify ZIKV-specific and ZIKV/DENV cross-reactive epitopes and demonstrate both an altered immunodominance pattern in the DENV-immune setting relative to naive, as well as a protective role for epitope-specific CD8+ T cells against ZIKV. These results have important implications for ZIKV vaccine development and provide a mouse model for evaluating anti-ZIKV CD8+ T cell responses of human relevance.

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.

Besides superconductivity, copper-oxide high temperature superconductors are susceptible to other types of ordering. We use scanning tunneling microscopy and resonant elastic x-ray scattering measurements to establish the formation of charge ordering in the high-temperature superconductor Bi2Sr2CaCu2O8+x. Depending on the hole concentration, the charge ordering in this system occurs with the same period as those found in Y-based or La-based cuprates, and displays the analogous competition with superconductivity. These results indicate the similarity of charge organization competing with superconductivity across different families of cuprates. We observe this charge ordering to leave a distinct electron-hole asymmetric signature (and a broad resonance centered at +20 meV) in spectroscopic measurements, thereby indicating that it is likely related to the organization of holes in a doped Mott insulator., preprint version, 12 pages, 3 figures. Supplement: 8 pages, 9 figures

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 α-RuCl_{3}, we observe spin-wave spectra with a gap of ∼2 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 Γ 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=-6.8 meV and Γ=9.5 meV. These results demonstrate explicitly that Kitaev physics is realized in real materials.

Several Zika virus (ZIKV) vaccines designed to elicit protective antibody (Ab) responses are currently under rapid development, but the underlying mechanisms that control the magnitude and quality of the Ab response remain unclear. Here, we investigated the CD4+ T cell response to primary intravenous and intravaginal infection with ZIKV. Using the LysMCre+Ifnar1fl/fl (myeloid type I IFN receptor-deficient) C57BL/6 mouse models, we identified six I-Ab-restricted ZIKV epitopes that stimulated CD4+ T cells with a predominantly cytotoxic Th1 phenotype in mice primed with ZIKV. Intravenous and intravaginal infection with ZIKV effectively induced follicular helper and regulatory CD4+ T cells. Treatment of mice with a CD4+ T cell-depleting Ab reduced the plasma cell, germinal center B cell, and IgG responses to ZIKV without affecting the CD8+ T cell response. CD4+ T cells were required to protect mice from a lethal dose of ZIKV after infection intravaginally, but not intravenously. However, adoptive transfer and peptide immunization experiments showed a role for memory CD4+ T cells in ZIKV clearance in mice challenged intravenously. These results demonstrate that CD4+ T cells are required mainly for the generation of a ZIKV-specific humoral response but not for an efficient CD8+ T cell response. Thus, CD4+ T cells could be important mediators of protection against ZIKV, depending on the infection or vaccination context., Author summary Several vaccine candidates are currently under development for Zika virus (ZIKV) infection, which causes life-threatening neurologic diseases, including congenital Zika syndrome in neonates and Guillain-Barré syndrome in adults. However, the mechanisms by which the adaptive immune system contributes to protection against ZIKV have not been fully investigated. In this report, we used mouse models of systemic and genital mucosal infection with ZIKV to evaluate the role of CD4+ T cells in regulating antiviral humoral and CD8+ T cell responses and in controlling ZIKV infection. We first defined the antigen specificity and phenotype of the CD4+ T cell response to ZIKV and then demonstrated that CD4+ T cells are required for inducing humoral, but not CD8+ T cell, responses in ZIKV-primed mice. CD4+ T cells were also required for local control of ZIKV burden in mice infected intravaginally. Although CD4+ T cells are not necessary for the control of primary ZIKV infection via the intravenous route, CD4+ T cells can confer protection against lethal intravaginal ZIKV challenge. Our results support ZIKV vaccine strategies that induce a protective CD4+ T cell response to ZIKV.

Zika virus (ZIKV) is an emerging mosquito-borne flavivirus linked to devastating neurologic diseases. Immune responses to flaviviruses may be pathogenic or protective. Our understanding of human immune responses to ZIKV in vivo remains limited. Therefore, we performed a longitudinal molecular and phenotypic characterization of innate and adaptive immune responses during an acute ZIKV infection. We found that innate immune transcriptional and genomic responses were both cell type- and time-dependent. While interferon stimulated gene induction was common to all innate immune cells, the upregulation of important inflammatory cytokine genes was primarily limited to monocyte subsets. Additionally, genomic analysis revealed substantial chromatin remodeling at sites containing cell-type specific transcription factor binding motifs that may explain the observed changes in gene expression. In this dengue virus-experienced individual, adaptive immune responses were rapidly mobilized with T cell transcriptional activity and ZIKV neutralizing antibody responses peaking 6 days after the onset of symptoms. Collectively this study characterizes the development and resolution of an in vivo human immune response to acute ZIKV infection in an individual with pre-existing flavivirus immunity., Author summary Zika virus (ZIKV) is an emerging flaviviral infection that causes significant clinical disease. It is estimated that approximately one half of the world’s population is at risk for ZIKV infection. There are only a limited number of studies describing the human immune response to ZIKV infection. Carlin et al. combined conventional and genomic approaches to longitudinally analyze the innate and adaptive immune responses to acute ZIKV infection and its resolution in a person who was infected while traveling in Venezuela during the 2016 ZIKV epidemic year. Genome-wide sequencing in individual cell types revealed that although many populations respond to interferon stimulation, only specific cell populations within peripheral blood mononuclear cells upregulate important inflammatory cytokine gene expression. Additionally, analysis of open chromatin using ATAC-seq suggests that chromatin remodeling at sites containing cell-type specific transcription factor binding motifs may help us understand changes in gene expression. Consistent with previous reports, this individual with prior exposure to dengue virus (DENV), rapidly developed neutralizing anti-ZIKV responses that were cross-reactive with multiple DENV serotypes. Collectively this study combines traditional and genomic approaches to characterize the cell-type specific development of an in vivo human immune response to acute ZIKV infection.

Topological superconductors are a very interesting and frontier topic in condensed matter physics. Despite the tremendous efforts in exploring topological superconductivity, its presence is however still under heavy debate. The Dirac electrons have been proven to exist on the surface of a topological insulator. It remains unclear whether and how the Dirac electrons fall into Cooper pairing in an intrinsic superconductor with the topological surface states. Here we show the systematic study of scanning tunnelling microscope/spectroscopy on the possible topological superconductor SrxBi2Se3. We first demonstrate that only the intercalated Sr atoms can induce superconductivity. Then we show the full superconducting gaps without any in-gap density of states as expected theoretically for a bulk topological superconductor. Finally, we find that the surface Dirac electrons will simultaneously condense into the superconducting state within the superconducting gap. This vividly demonstrates how the surface Dirac electrons are driven into Cooper pairs., Whether and how the Dirac electrons can be driven into superconducting state remains unclear. Here, Du et al. present systematic study to demonstrate the Dirac electrons condensing into Cooper pairs on the surface of a possible topological superconductor Sr x Bi2Se3.

Surface reactivity is important in modifying the physical and chemical properties of surface-sensitive materials, such as the topological insulators. Even though many studies addressing the reactivity of topological insulators towards external gases have been reported, it is still under heavy debate whether and how the topological insulators react with ${\mathrm{H}}_{2}\mathrm{O}$. Here, we employ scanning tunneling microscopy to directly probe the surface reaction of $\mathrm{B}{\mathrm{i}}_{2}\mathrm{T}{\mathrm{e}}_{3}$ towards ${\mathrm{H}}_{2}\mathrm{O}$. Surprisingly, it is found that only the top quintuple layer is reactive to ${\mathrm{H}}_{2}\mathrm{O}$, resulting in a hydrated Bi bilayer as well as some Bi islands, which passivate the surface and prevent subsequent reaction. A reaction mechanism is proposed with ${\mathrm{H}}_{2}\mathrm{Te}$ and hydrated Bi as the products. Unexpectedly, our study indicates that the reaction with water is intrinsic and not dependent on any surface defects. Since water inevitably exists, these findings provide key information when considering the reactions of $\mathrm{B}{\mathrm{i}}_{2}\mathrm{T}{\mathrm{e}}_{3}$ with residual gases or atmosphere.

Topological superconductor is a very interesting and frontier topic in condensed matter physics1. Despite the tremendous efforts in exploring the topological superconductivity, its presence is however still under heavy debates. The Dirac electrons are supposed to exist in a thin layer of the surface of a topological insulator. Due to the finite spin-orbital coupling, these electrons will have a spin-momentum locking effect. In this case, the superfluid with the spin singlet Cooper pairing is not completely comforted by the Dirac electrons. It thus remains unclear whether and how the Dirac electrons fall into Cooper pairing in an intrinsic superconductor with the topological surface states. In this work, we show the systematic study of scanning tunneling microscope/spectroscopy on the possible topological superconductor SrxBi2Se3. We first show that only the intercalated (or inserted), not the substituted Sr atoms can induce superconductivity. Then we show the full superconducting gaps without any abnormal in-gap density of states as expected theoretically for the bulk topological superconductivity. However, we find that the surface Dirac electrons will simultaneously condense into the superconducting state when the energy is smaller than the bulk superconducting gap. This vividly demonstrates how the surface Dirac electrons are driven into Cooper pairs., 28 pages, 7 figures, including Supplementary Information

It has recently been demonstrated that dynamical magnetic correlations measured by neutron scattering in iron chalcogenides can be described with models of short-range correlations characterized by particular choices of four-spin plaquettes, where the appropriate choice changes as the parent material is doped towards superconductivity. Here we apply such models to describe measured maps of magnetic scattering as a function of two-dimensional wave vectors obtained for optimally superconducting crystals of ${\mathrm{FeTe}}_{1\ensuremath{-}x}{\mathrm{Se}}_{x}$. We show that the characteristic antiferromagnetic wave vector evolves from that of the bicollinear structure found in underdoped chalcogenides (at high temperature) to that associated with the stripe structure of antiferromagnetic iron arsenides (at low temperature); these can both be described with the same local plaquette, but with different interplaquette correlations. While the magnitude of the low-energy magnetic spectral weight is substantial at all temperatures, it actually weakens somewhat at low temperature, where the charge carriers become more itinerant. The observed change in spin correlations is correlated with the dramatic drop in the electronic scattering rate and the growth of the bulk nematic response upon cooling. Finally, we also present powder neutron diffraction results for lattice parameters in ${\mathrm{FeTe}}_{1\ensuremath{-}x}{\mathrm{Se}}_{x}$ indicating that the tetrahedral bond angle tends to increase towards the ideal value upon cooling, in agreement with the increased screening of the crystal field by more itinerant electrons and the correspondingly smaller splitting of the Fe $3d$ orbitals.

It's the Oxygens Scanning tunneling microscopy of cuprate high-temperature superconductors has revealed surprising inhomogeneity of the energy scales known as the superconducting gap, pseudogap, and the critical temperature. Some of these effects have been correlated with chemical disorder of the materials caused by doping, but, because of technical limitations, only the dopants in a limited energy range have been imaged. Zeljkovic et al. (p. 320 ) extend this range to reveal the positions of the remaining oxygen defects in Bi 2+y Sr 2-y CaCu 2 O 8+x .

A complicating factor in unraveling the theory of high-temperature (high-Tc) superconductivity is the presence of a "pseudogap" in the density of states, whose origin has been debated since its discovery [1]. Some believe the pseudogap is a broken symmetry state distinct from superconductivity [2-4], while others believe it arises from short-range correlations without symmetry breaking [5,6]. A number of broken symmetries have been imaged and identified with the pseudogap state [7,8], but it remains crucial to disentangle any electronic symmetry breaking from pre-existing structural symmetry of the crystal. We use scanning tunneling microscopy (STM) to observe an orthorhombic structural distortion across the cuprate superconducting Bi2Sr2Can-1CunO2n+4+x (BSCCO) family tree, which breaks two-dimensional inversion symmetry in the surface BiO layer. Although this inversion symmetry breaking structure can impact electronic measurements, we show from its insensitivity to temperature, magnetic field, and doping, that it cannot be the long-sought pseudogap state. To detect this picometer-scale variation in lattice structure, we have implemented a new algorithm which will serve as a powerful tool in the search for broken symmetry electronic states in cuprates, as well as in other materials.

Background Dengue virus (DENV), the most widely prevalent arbovirus, continues to be a threat to human health in the tropics and subtropics. Early and rapid detection of DENV infection during the acute phase of illness is crucial for proper clinical patient management and preventing the spread of infection. The aim of the current study was to develop a specific, sensitive, and robust reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) assay for detection and differentiation of DENV1-4 serotypes. Results The method detection primers, which were designed to target the different DENV serotypes, were identified by inspection of multiple sequence alignments of the non-structural protein (NS) 2A of DENV1, NS4B of DENV2, NS4A of DENV3 and the 3′ untranslated region of the NS protein of DENV4. No cross-reactions of the four serotypes were observed during the tests. The detection limits of the DENV1-4-specific RT-LAMP assays were approximately 10-copy templates per reaction. The RT-LAMP assays were ten-fold more sensitive than RT-PCR or real-time PCR. The diagnostic rate was 100 % for clinical strains of DENV, and 98.9 % of the DENV-infected patients whose samples were tested were detected by RT-LAMP. Importantly, no false-positives were detected with the new equipment and methodology that was used to avoid aerosol contamination of the samples. Conclusion The RT-LAMP method used in our study is specific, sensitive, and suitable for further investigation as a useful alternative to the current methods used for clinical diagnosis of DENV1-4, especially in hospitals and laboratories that lack sophisticated diagnostic systems.

I present a brief overview on the interplay between magnetism and superconductivity in one of the Fe-based superconductor systems, Fe 1 + y Te 1 − x Se x , where the research of our group has centered. The parent compound Fe 1 + y Te is an antiferromagnet; with Se doping, antiferromagnetic order is suppressed, followed by the appearance of superconductivity; optimal superconductivity is achieved when x ∼ 50 % , with a superconducting temperature T c of ∼ 15 K. The parent compound has an in-plane magnetic ordering wave vector around (0.5, 0) (using the tetragonal notation with two Fe atoms per cell). When Se concentration increases, the spectral weight appears to be shifted to the wave vector around (0.5, 0.5), accompanying the optimization of superconductivity. A neutron-spin resonance has been observed around (0.5, 0.5) below T c , and is suppressed, along with superconductivity, by an external magnetic field. Taking these evidences into account, it is concluded that magnetism and superconductivity in this system couple to each other closely—while the static magnetic order around (0.5, 0) competes with superconductivity, the spin excitations around (0.5, 0.5) may be an important ingredient for it. I will also discuss the nature of magnetism and substitution effects of 3 d transition metals.

Electronic Raman scattering measurements have been performed on hole doped copper oxide superconductors as a function of temperature and doping level. In the superconducting state coherent Bogoliubov quasiparticles develop preferentially over the nodal region in the underdoped regime. We can then define the fraction of coherent Fermi surface, $f_c$ around the nodes for which quasiparticles are well defined and superconductivity sets in. We find that $f_c$ is doping dependent and leads to the emergence of two energy scales. We then establish in a one single gap shem, that the critical temperature $T_{c} \propto f_{c}\Delta_{max}$ where $\Delta_{max}$ is the maximum amplitude of the d-wave superconducting gap. In the normal state, the loss of antinodal quasiparticles spectral weight detected in the superconducting state persists and the spectral weight is only restored above the pseudogap temperature $T*$. Such a dichotomy in the quasiparticles dynamics is then responsible for the emergence of the two energy scales in the superconducting state and the appearance of the pseudogap in the normal state. We propose a 3D phase diagram where both the temperature and the energy phase diagrams have been plotted together. We anticipate that the development of coherent excitations on a restricted part of the Fermi surface only is a general feature in high $T_c$ cuprate superconductors as the Mott insulating is approaching., Comment: 40 pages, 19 figures some new references and comments have been added with respect to the first version of march 30th