The CsCr3Sb5 exhibits superconductivity in close proximity to a density-wave (DW) like ground state at ambient pressure1, however details of the DW is still elusive. Using first-principles density-functional calculations, we found its ground state to be a 4 × 2 altermagnetic spin-density-wave (SDW) at ambient pressure, with an averaged effective moment of ~ 1.7μB/Cr. The magnetic long range order is coupled to the lattice, generating 4a0 structural modulation. Multiple competing SDW phases are present and energetically close, suggesting strong magnetic fluctuation at finite temperature. The electronic states near Fermi level are dominated by Cr-3d orbitals, and the kagome flat bands are closer to the Fermi level than those in the AV3Sb5 family in paramagnetic state. When external pressure is applied, the energy differences between competing orders and structural modulations are suppressed. Yet, the magnetic fluctuation remains present and important even at high pressure because the high-symmetry kagome lattice is unstable in nonmagnetic phase up to 30 GPa. Our results suggest the crucial role of magnetism to stabilize the crystal structure, under both ambient and high pressure. Recent work reported a kagome metal CsCr3Sb5 with frustrated magnetism, density-wave-like order at ambient pressure, and superconductivity under pressure. Using first principles calculations, Xu et al. reveal an altermagnetic spin-density-wave ground state at ambient pressure and phase competition with pressure.

The spin dynamics and electronic orders of the kagome system at different filling levels stand as an intriguing subject in condensed matter physics. By first-principles calculations and random phase approximation analyses, we investigate the spin fluctuations and superconducting instabilities in kagome phase of CsCr3Sb5 under high pressure. At the filling level slightly below the kagome flat bands, our calculations reveal strong antiferromagnetic spin fluctuations in CsCr3Sb5, together with a leading s±-wave and a competing (dxy, d_x^2-y^2 )-wave superconducting order. Unlike the general intuition that the flat bands are closely related to the ferromagnetic correlations, here we propose a sublattice-momentum-coupling-driven mechanism for the antiferromagnetic fluctuations enhanced from the unoccupied flat bands. The mechanism is generally applicable to kagome systems where the Fermi level intersects near the flat bands, offering a new perspective for future studies of geometrically frustrated systems. The authors theoretically investigate the spin fluctuations and superconducting instabilities in the kagome phase of CsCr3Sb5 under high pressure. They find that incipient flat bands play a role in enhancing antiferromagnetic fluctuations, which in turn mediate the competing s-wave and d-wave superconducting ordering.

We theoretically propose Ac_3Ni_2O_7, La_2BaNi_2O_6F, and La_2SrNi_2O_6F compounds to be benchmark materials for bilayer nickelate superconductivity. The stable phase of Ac_3Ni_2O_7 and La_2BaNi_2O_6F are found to be I4/mmm without the lattice distortion caused by octahedra rotation at ambient pressure, where as the lattice distortion in La_2SrNi_2O_6F can be suppressed with relatively small external pressure of 4 GPa. The magnetism, electronic structure and spin susceptibilities of Ac_3Ni_2O_7 are extremely close to those of La_3Ni_2O_7 at 30 GPa. The ground state of La_2BaNi_2O_6F and La_2SrNi_2O_6F are antiferromagnetically coupled checkerboard bilayer with sizable magnetic moment on Ni. In addition, the inter-layer coupling J_⊥ between Ni-bilayers in La_2BaNi_2O_6F or La_2SrNi_2O_6F is only ∼ 1/10 of that in Ac_3Ni_2O_7 or La_3Ni_2O_7 at 30 GPa. We argue that these compounds may serve as superconducting candidates at ambient pressure and can be employed to testify theoretical proposals for bilayer nickelate superconductivity.

The antiferromagnetism in transition metal compounds is mostly mediated by the bridging anions through a so-called superexchange mechanism. However, in materials like normal spinels AB2X4 with local moments only at the A site, such an anion-mediated superexchange needs to be modified. Here we report a new spinel compound Co1+xIr2-xS4 (x = 0.3). The physical property measurements strongly suggest an antiferromagnetic-like transition at 292 K in the Co(A) diamond sublattice. The first-principle calculations reveal that the nearest-neighbor Co(A) spins align antiferromagnetically with an ordered magnetic moment of 1.67 mu B, smaller than the expected S = 3/2 for Co2+. In the antiferromagnetic state, there exists an inter-cation charge-transfer gap between the nonbonding Ir-t2g orbitals at the valence band maximum and the Co-S antibonding molecular orbitals at the conduction band minimum. The small charge transfer energy significantly enhances the virtual hopping between these two states, facilitating a robust long-range superexchange interaction between two neighboring CoS4 complexes, which accounts for the high N & eacute;el temperature in Co1+xIr2-xS4. This inter-cation charge transfer mediated magnetic interaction expands the traditional superexchange theory, which could be applicable in complex magnetic materials with multiple cations.

We report the physical properties of ThRu 3 Si 2 featured with distorted Ru kagome lattice. The combined experiments of resistivity, magnetization and specific heat reveal bulk superconductivity with T c = 3.8 K. The specific heat jump and calculated electron–phonon coupling indicate a moderate coupled BCS superconductor. In comparison with LaRu 3 Si 2 , the calculated electronic structure in ThRu 3 Si 2 shows an electron-doping effect with electron filling lifted from 100 meV below flat bands to 300 meV above it. This explains the lower superconducting transition temperature and weaker electron correlations observed in ThRu 3 Si 2 . Our work suggests the T c and electronic correlations in the kagome superconductor could have an intimate connection with the flat bands.

Superconductivity in a highly correlated kagome system has been theoretically proposed for years (refs. 1-5), yet the experimental realization is hard to achieve6,7. The recently discovered vanadium-based kagome materials8, which exhibit both superconductivity9-11 and charge-density-wave orders12-14, are nonmagnetic8,9 and weakly correlated15,16. Thus these materials are unlikely to host the exotic superconductivity theoretically proposed. Here we report the discovery of a chromium-based kagome metal, CsCr3Sb5, which is contrastingly featured with strong electron correlations, frustrated magnetism and characteristic flat bands close to the Fermi level. Under ambient pressure, this kagome metal undergoes a concurrent structural and magnetic phase transition at 55 K, with a stripe-like 4a0 structural modulation. At high pressure, the phase transition evolves into two transitions, possibly associated with charge-density-wave and antiferromagnetic spin-density-wave orderings. These density-wave-like orders are gradually suppressed with pressure and, remarkably, a superconducting dome emerges at 3.65-8.0 GPa. The maximum of the superconducting transition temperature, Tcmax = 6.4 K, appears when the density-wave-like orders are completely suppressed at 4.2 GPa, and the normal state exhibits a non-Fermi-liquid behaviour, reminiscent of unconventional superconductivity and quantum criticality in iron-based superconductors17,18. Our work offers an unprecedented platform for investigating superconductivity in correlated kagome systems.

We report the synthesis, crystal structure, and physical properties of a novel ternary compound, Th2Cu4As5. The material crystallizes in a tetragonal structure with lattice parameters a = 4.0639(3) Å and c = 24.8221(17) Å. Its structure can be described as an alternating stacking of fluorite-type Th2As2 layers with antifluorite-type double-layered Cu4As3 slabs. The measurement of electrical resistivity, magnetic susceptibility, and specific heat reveals that Th2Cu4As5 undergoes bulk superconducting transition at 4.2 K. Additionally, all these physical quantities exhibit anomalies at 48 K, accompanied by a sign change in the Hall coefficient, suggesting a charge-density-wave-like (CDW) phase transition. Drawing from both experimental data and band calculations, we propose that the superconducting and CDW-like phase transitions are, respectively, associated with the Cu4As3 slabs and the As plane in the Th2As2 layers.

Unconventional superconductivity (USC) in a highly correlated kagome system has been theoretically proposed for years, yet the experimental realization is hard to achieve. The recently discovered vanadium-based kagome materials, which exhibit both superconductivity and charge density wave (CDW) orders, are nonmagnetic and weakly correlated, thus unlikely host USC as theories proposed. Here we report the discovery of a chromium-based kagome metal, CsCr$_3$Sb$_5$, which is contrastingly characterised by strong electron correlations, frustrated magnetism, and characteristic flat bands close to the Fermi level. Under ambient pressure, it undergoes a concurrent structural and magnetic phase transition at 55 K, accompanying with a stripe-like $4a_0$ structural modulation. At high pressure, the phase transition evolves into two transitions, probably associated with CDW and antiferromagnetic spin-density-wave orderings, respectively. These density-wave (DW)-like orders are gradually suppressed with pressure and, remarkably, a superconducting dome emerges at 3.65-8.0 GPa. The maximum of the superconducting transition temperature, $T_\mathrm{c}^{\mathrm{max}}=$ 6.4 K, appears when the DW-like orders are completely suppressed at 4.2 GPa, and the normal state exhibits a non-Fermi-liquid behaviour, reminiscent of USC and quantum criticality in iron-based superconductors. Our work offers an unprecedented platform for investigating possible USC in a correlated kagome system.

Kagome materials exhibit many novel phenomena emerging from the interplay between lattice geometry, electronic structure, and topology. A prime example is the vanadium-based kagome materials AV3Sb5 (A = K, Rb, and Cs) with superconductivity and unconventional charge-density wave (CDW). More interestingly, the substitution of vanadium by chromium further introduces magnetism and enhances the correlation effect in CsCr3Sb5 which likewise exhibits superconductivity under pressure and competing density-wave state. Here we systematically investigate the electronic structure of CsCr3Sb5 using high-resolution angle-resolved photoemission spectroscopy (APRES) and ab-initio calculations. Overall, the measured electronic structure agrees with the theoretical calculation. Remarkably, Cr 3d orbitals exhibit incoherent electronic states and contribute to incipient flat bands close to the Fermi level. The electronic structure shows a minor change across the magnetic transition at 55 K, suggesting a weak interplay between the local magnetic moment and itinerant electrons. Furthermore, we reveal a drastic enhancement of the electron scattering rate across the magnetic transition, which is relevant to the semiconducting-like transport property of the system at high temperatures. Our results suggest that CsCr3Sb5 is a strongly correlated Hund's metal with incipient flat bands near the Fermi level, which provides an electronic basis for understanding its novel properties in comparison to the non-magnetic and weakly correlated AV3Sb5.

Abstract Striatin‐interacting phosphatases and kinases (STRIPAKs) are evolutionarily conserved supramolecular complexes that control various important cellular processes such as signal transduction and development. However, the role of the STRIPAK complex in pathogenic fungi remains elusive. In this study, the components and function of the STRIPAK complex were investigated in Fusarium graminearum, an important plant‐pathogenic fungus. The results obtained from bioinformatic analyses and the protein–protein interactome suggested that the fungal STRIPAK complex consisted of six proteins: Ham2, Ham3, Ham4, PP2Aa, Ppg1, and Mob3. Deletion mutations of individual components of the STRIPAK complex were created, and observed to cause a significant reduction in fungal vegetative growth and sexual development, and dramatically attenuae virulence, excluding the essential gene PP2Aa. Further results revealed that the STRIPAK complex interacted with the mitogen‐activated protein kinase Mgv1, a key component in the cell wall integrity pathway, subsequently regulating the phosphorylation level and nuclear accumulation of Mgv1 to control the fungal stress response and virulence. Our results also suggested that the STRIPAK complex was interconnected with the target of rapamycin pathway through Tap42‐PP2A cascade. Taken together, our findings revealed that the STRIPAK complex orchestrates cell wall integrity signalling to govern the fungal development and virulence of F. graminearum and highlighted the importance of the STRIPAK complex in fungal virulence.

- We report on the synthesis, crystal structure, physical properties, and first-principles calculations of a new borocarbide ThNiBC. The new compound was synthesized by an arc-melting method, crystallizing in a tetragonal LuNiBC-type structure with an exceptionally low axial ratio of c/a = 1.98. The physical property measurements indicate that it is a Pauli-paramagnetic metal with significant electron-electron scattering. Bulk superconductivity at Tc = 0.7 K is demon-strated with zero electrical resistivity, Meissner effect, and specific-heat jump. The first-principles calculations reveal a relatively low density of states at the Fermi level with multiple electron-type Fermi surfaces.Copyright (c) 2023 EPLA

Quasi-one-dimensional(Q1D) Cr-based pnictide K 2 Cr 3 As 3 exhibits superconductivity probably with spin-triplet pairing. It is of fundamental importance to explore the parent compound from which superconductivity emerges. Here we report the synthesis,crystal structure, physical properties, and density functional theory(DFT) calculations of(nearly) fully hydrogenized K 2 Cr 3 As 3 H.It is found that the intercalation of hydrogen in K 2 Cr 3 As 3 leads to absence of metallicity as well as superconductivity. An antiferromagnetic transition nearby room temperature is evidenced from the measurements of magnetic susceptibility and heat capacity.The antiferromagnetic insulating state can be reproduced by the DFT calculations, which show a novel non-collinear co-planar magnetic order. Our result sheds light on the mechanism of unconventional superconductivity in Q1D Cr-based superconductors.

Chemical doping leads to a strong enhancement of superconductivity in the topological transition metal silicide W 5 Si 3 .

A new noncentrosymmetric superconductor, W 4 IrC 1− x , has been synthesized and characterized.

We report synthesis, crystal structure, and physical properties of Sr2Cr2AsO3. The new compound crystallizes in a Sr2GaO3CuS-type structure with two distinct Cr sites, Cr(1) in the perovskite-like block layers of "Sr3Cr2O6" and Cr(2) in the ThCr2Si2-type layers of "SrCr2As2". An inter-block-layer charge transfer is explicitly evidenced, which dopes electrons in the CrO2 planes and simultaneously dopes holes into the CrAs layers. Measurements of electrical resistivity, magnetization, and specific heat, in combination with density-functional theoretical calculations, indicate that the title material is an antiferromagnetic metal. The Cr(2) magnetic moments in the CrAs layers order at 420 K, while the Cr(1) spins in the CrO2 planes show quasi-two-dimensional magnetism with long-range ordering below 80 K. Both Néel temperatures are significantly reduced, compared with those of the cousin material Sr2Cr3As2O2, probably due to the intrinsic charge-carrier doping. Complex re-entrant magnetic transitions with a huge magnetic hysteresis were observed at low temperatures.

We have investigated the As-doping effect in the newly discovered kagome superconductor CsV3Sb5 via measurements of x-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat. Our results show that partial substitution of Sb with As leads to shrinkage of the c lattice, which effectively applies a chemical pressure in the system. The solubility of As atoms is about 2.3% for single crystals grown by the self-flux method. In the As-doped single crystal CsV3(Sb0.977As0.023)(5), the charge-density-wave (CDW) transition temperature T-CDW is suppressed from 94 to 83 K, and the superconducting transition temperature Tc is enhanced from 2.5 to 3.6 K. Furthermore, the residual resistivity ratio is significantly reduced, and the magnetoresistance with magnetic field along the c axis decreases by nearly one order of magnitude, indicating substantial disorder scattering induced by the As doping. The anomalous Hall effect (AHE) is only observed below T-CDW, indicating the intimate relationship between CDW and AHE. We found that the As-doping effect on T-c and T-CDW is basically equivalent to the hydrostatic pressure effect at 0.2 GPa.

We report the results of structural and physical studies on the MoReRuCx medium-entropy alloys (MEAs) with x varying from 0 to 0.20. In the whole x range, a single hexagonal phase is formed. The variation of lattice parameters indicates that carbon atoms are located at the interstitial site for x <= 0.10 while occupy both the interstitial and substitutional sites at higher x values, which is corroborated by the x-ray photonelectron spectroscopy (XPS) results. Moreover, the resistivity, magnetic and thermodynamic measurements evidence that these MEAs are bulk fully gapped superconductors. In particular, the transition temperature Tc displays a dome-like dependence on carbon content with a maximum of 9.62 K at x = 0.05, whereas a maximal zero-temperature upper critical field Bc2(0) of 10.5 T is achieved at x = 0.10. For all MEAs, the specific heat data reveal the existence of an inhomogeneous superconducting state, which is discussed in relation to the chemical inhomogeneity and strong atomic disorder. In addition, we show that the key factors that control superconductivity are essentially the same for both MoReRuCx and ReCx, despite their very different Tc values. Our work not only provides the first series of interstitial MEAs with a hexagonal structure, but also demonstrates a feasible way to tune the superconductivity in multicomponent alloys. (c) 2021 Elsevier B.V. All rights reserved.

We report a tetragonal polymorph of BaFe2S2O synthesized under high pressures. This beta-BaFe2S2O phase is structurally characterized by two-dimensional Fe2O square nets that are sandwiched by sulfur atomic layers. The electrical, magnetic, and thermodynamic measurements indicate that it is an antiferromagnetic insulator with a Neel temperature of 121 K. A successive magnetic transition at similar to 40 K is observed, possibly associated with spin canting due to Dzyaloshinskii-Moriya interactions. Density functional theory based calculations reveal Mott localization driven by the on-site electron-electron Coulomb repulsion. The calculations also suggest a noncollinear Fe2+-spin structure with two-k [k(1) = (1/2, 0, 1/2) and k(2) = (0, 1/2, 1/2)] propagation vectors, primarily due to the magnetocrystalline anisotropy as well as the next-nearest-neighbor superexchange interactions mediated by oxygen and sulfur anions, respectively.

We present experimental and theoretical investigations for the cobalt thiospinel Co3S4-8. High-quality samples of Co3S4-8 (8 -0.1) were prepared so as to measure their intrinsic properties. The measurements of magnetic susceptibility, specific heat, and electrical transport consistently indicate an antiferromagnetic transition at -60 K, which is attributed to long-range magnetic ordering in the Co(A) (A-site Co ions) diamond sublattice. In addition, there exists a short-range magnetic ordering at around 120 K associated with the magnetic frustrations. The high-temperature magnetic susceptibility obeys Curie-Weiss law, from which a small effective magnetic moment of 1.0 mu B per formula unit is yielded. The main experimental results can be interpreted by the density-functional-theory calculations with a Hubbard U correction of -0.5 eV. Combining the experimental measurements with the theoretical calculations, we conclude that Co3S4 represents a rare example of itinerant-electron diamond-lattice antiferromagnet with moderate electron correlations.

We derived explicit expressions of symmetry operators on Wannier basis, and implemented these operators in WannSymm software. Based on this implementation, WannSymm can i) symmetrize the real-space Hamiltonian output from Wannier90 code, ii) generate symmetry operators of the little group at a specific k-point, and iii) perform symmetry analysis for Wannier band structure. In general, symmetrized Hamiltonians yield improved results compared with the original ones when they are employed for nodal structure searching, surface Green’s function calculations, and other model calculations.