These years, kagome materials with 1:1 stoichiometry have garnered increasing attention, among which FeSn, CoSn, and FeGe have been the focus of current studies. However, all of them are antiferromagnetic, thereby hindering the observation of superconductivity and other novel physical properties. Here, we predict a novel 1:1 kagome metal VSn, which is an intrinsic charge density wave (CDW) material. Interestingly, with increasing pressure or doping concentration, the CDW order is progressively suppressed, followed by the emergence of superconductivity characterized by a non-monotonic transition temperature that exhibits a rare anti-dome-shaped dependence. Above a critical threshold, a reentrance of the CDW phase occurs. The anti-dome superconductivity originates from the first hardening and then softening of phonon modes, together with band reconstruction. Crucially, VSn retains nontrivial topological properties across the entire superconducting regime, a feature of paramount importance for realizing robust topological superconductivity. These intertwined CDW, superconductivity, and topological phenomena elucidate the correlations among multiple quantum states in VSn. Therefore, this research paves the way for for designing 1:1 kagome superconducting topological metals and establishes a platform for exploring the interplay of multiple phases in kagome systems.

Abstract The successful synthesis of monolayer MoSi$_2$N$_4$ [Science 369, 670 (2020)] has established Si-N layer passivation as an effective modification strategy for two-dimensional (2D) materials. Inspired by this, we propose a novel 2D material, ZnOSiN, obtained by passivating graphene-like ZnO ($g$-ZnO) with a Si-N layer. Using first-principles calculations, we systematically investigate its crystal structure, electronic structure, electron–phonon coupling (EPC), superconductivity, and charge density wave (CDW) behavior. The Si-N passivation induces a semiconductor-to-metal transition in $g$-ZnO and a near-free electron gas (NFEG) appears beneath Zn atoms, which results in a phonon-mediated superconductor with a critical temperature ($T_{c}$) of 10.6 K. The EPC originates primarily from coupling between Zn-$s$ orbital electrons, NFEG and the lowest-frequency acoustic phonon modes dominated by Zn atoms. Under 6$\%$ biaxial tensile strain, $T_{c}$ increases to 14.5 K, accompanied by a large EPC constant $\lambda$ of 3.99. At 7$\%$ strain, an imaginary frequency emerges in the lowest acoustic branch of the phonon dispersion, signaling CDW instability. Analysis based on Lindhard electron susceptibility and EPC reveals that this CDW is jointly driven by Fermi-surface nesting and EPC. Our approach not onlytransforms g-ZnO into a superconductor but also provides a versatile platform for investigating 2D superconductivity and CDW.

In recent years, metal hydride superconductors have attracted extensive attention. However, most hydride superconductors exhibit superconductivity only under high pressure. Therefore, achieving superconductivity in metal hydrides at low or even ambient pressures has drawn considerable attention. Here, based on first-principles calculations, we systematically investigate the electronic, topological, and superconducting properties of three-dimensional (3D) transition metal cubic hydride CrH. The calculated superconducting transition temperature (T c) is 13.3 K, which primarily originates from the coupling between the d-orbital electrons of Cr and the low-frequency phonon modes softened by Cr-H vibrations. In addition, CrH exhibits a nontrivial band topology. The predicted CrH enriches the family of metal hydride superconductors and provides an important platform for studying the physical properties of metal hydrides under ambient conditions.

In this work, we present a systematic investigation of the electronic structures, band topology, and intrinsic spin Hall effect (SHE) in the layered MAX carbides Mn+1AlCn (M = Nb, Ta; n = 1, 2, 3) and explore the correlation effects on the SHE. Our results show that this family of materials exhibits Dirac-band-crossing features near the Fermi level EF and forms nodal lines in the absence of spin-orbit coupling (SOC). When the SOC is included, the Dirac band crossings are fully gapped, resulting in nontrivial Z2 topological invariants (1;000) with a pair of surface states on the (001) plane. Notably, the multiple gapped Dirac points contribute to locally strong spin Berry curvatures, which lead to large spin Hall conductivities (SHCs) and spin Hall angles (0.02-0.62 at EF) for Tan+1AlCn (n = 1, 2, 3). Moreover, we also elucidate the impact of the Hubbard U correction on SHCs. Our findings suggest that Tan+1AlCn (n = 1, 2, 3) might represent intriguing layered Z2 topological metals with superior charge-to-spin conversion efficiency.

Recently, the films of the Ruddlesden-Popper (RP) nickelate superconductors, in which the (La,Pr)3Ni2O7 system exhibits a remarkable transition temperature Tc exceeding 40 K, were synthesized at ambient pressure. We systematically investigate the band structures and electronic correlation effects to identify the key factors controlling superconductivity and pathways to enhance Tc. Based on density functional theory (DFT) calculations, we construct a bilayer two-orbital ( 3d_3z^2-r^2 and 3d_x^2-y^2 ) tight-binding model for a series of in-plane compression mimicking the substrate effect. We find the band energy at the M point drops with the compression, leading to an increase in the density of states at the Fermi level, in stark contrast to the behavior of the bulk under pressure. We then apply the functional renormalization group (FRG) method to study the electronic correlation effect on the superconductivity. We find the s±-wave pairing symmetry remains robust in the films, the same as the bulk. But somewhat surprisingly, for the films, we find Tc can be enhanced by reducing the in-plane lattice constant, increasing the out-of-plane lattice constant, or further electron-doping. These findings are consistent with the itinerant picture of the superconductivity induced by spin-fluctuations and provide theoretical support for further boosting Tc in future experiments.

Abstract The practical advancement of sodium-metal batteries (SMBs) is hindered by unstable anode/cathode interfaces and suboptimal ion transport kinetics. Traditional separators, functioning as passive elements, fail to effectively regulate ionic flux and interfacial chemistry, leading to low Na+ transference numbers, pronounced concentration polarization, and unstable electrode interphases. This study introduces a novel smart separator based on medium-entropy metal-organic framework (EMOF). By incorporating ion-confinement mechanisms within sub-nanochannels, it synergistically regulates Na+ transport and interfacial reaction kinetics. The EMOF separator establishes a hierarchical capillary system: macroscale channels ensure rapid electrolyte wettability, while nanoconfinement channels guide uniform Na+ flux distribution. Its multicomponent medium-entropy architecture endows channel surfaces with specific electrostatic environments that effectively anchor PF6− anions, elevating the Na+ transference number to 0.81. Significantly, this configuration further promotes PF6− decomposition, promoting the in-situ formation of inorganic-rich and stable electrode-electrolyte interphase layers. Leveraging these synergistic mechanisms, SMBs employing the EMOF separator in Na3V2(PO4)2O2F systems achieve an ultra-high energy density of 296.5 Wh kg−1 based on the mass of electrode materials, and outstanding fast-charging capability, maintaining 87.1% capacity retention even at 10 C rate, showcasing superior comprehensive performance. This work transcends the conventional paradigm of separators as inert barriers, establishing a new design framework for high-performance SMBs.

Kagome superconductors featuring topologically nontrivial band structures have attracted extensive research interest. FeSn and CoSn is an interesting kind of kagome material with intrinsic magnetism, which suppresses the emergence of superconductivity. Here, we theoretically predict a type of 1:1 kagome MSn (M = transition metal), which exhibits intrinsic superconductivity and nontrivial band topology by first-principles calculations. Among twenty-seven candidates, MSn (M = Mo, Hf, Nb, Ta, W, Ti) are theoretically identified as both dynamically and thermodynamically stable. Five nonmagnetic MSn (M = Mo, Hf, Nb, Ta, W) exhibit phononmediated superconductivity. Especially, the d orbital bands display Dirac points and van Hove singularities near the Fermi level, which contribute to the emergence of topology and the electron-phonon coupling (EPC). More interestingly, MoSn, HfSn, and NbSn show nontrivial topological band structure at the Fermi level. Thus, the predicted MSn establish a platform integrating superconductivity and topological order.

Recently, La3Ni2O7 thin film on the LaAlO3 substrate is shown to be superconducting, while the bulk La3Ni2O7 with the same in-plane lattice constant under pressure does not superconduct. This difference suggests the interlayer distance d_ Ni-Ni is crucial to control superconductivity, and its variation under pressure may tune the ground state sensitively. We investigate systematically the La3Ni2O7/LaAlO3 thin films in a reasonable range of d_ Ni-Ni, by a combination of the first-principle calculations and the singular-mode functional renormalization group. For smaller (larger) d_ Ni-Ni, the ground state is a C-type (G-type) spin density wave with spins coupled ferromagnetically (antiferromagnetically) across the two layers. Between the two phases, s_±-wave superconductivity emerges with dominant pairings between nickel 3d_3z^2-r^2 orbitals. The results explain the experimental superconductivity in the thin film under ambient pressure, and predict that the applied pressure will decrease the superconducting transition temperature, until the system enters the C-type spin density wave. Experimental verification would provide profound insights into the nature of electron correlations in this system, since the C-type spin density wave is achieved most naturally in the itinerant picture, while it would be hard in the local moment picture where spins are always coupled antiferromagnetically across the layers.

Inspired by the successful synthesis of two-dimensional (2D) MoSi2N4 and WSi2N4 [Y. L. Hong et al., Science 369, 670 (2020)], which demonstrates that Si-N layers can act as effective modification layers on 2D materials, we investigate superconductivity and charge density waves (CDWs) of hexagonal boron nitride (h-BN) passivated with a Si-N layer based on first-principles calculations. Our results demonstrate that h-BN undergoes a transition from an insulator to a phonon-mediated superconductor with the transition temperature (Tc) of 14.3 K when it is functionalized with a Si-N layer on one side. The electron-phonon coupling (EPC) of BN2Si is primarily attributed to the coupling between electrons in N-pz orbitals and the low-frequency in-plane vibrational modes of Si and N atoms, as well as higher-frequency out-of-plane vibration modes of N and B atoms. By applying 5% biaxial tensile strain, the EPC constant ) increases from 0.66 to 1.82, resulting in a significantly enhanced Tc of 34.9 K. However, when the biaxial tensile strain reaches 6%, an obvious soft mode emerges in the lowest acoustic branch of phonon curves, indicating the presence of a CDW. The origin of the instabilities is analyzed based on Lindhard electron susceptibility and the phonon linewidths, revealing that the CDW is driven by both Fermi-surface nesting and EPC. Thus, the predicted BN2Si presents a promising platform for exploring 2D superconductivity and CDWs.

Experimental studies have reported that nitrogen (N)-doped orthorhombic alpha-Mo2C exhibits a significant enhancement in its superconducting transition temperature (Tc). To elucidate the underlying mechanisms, we conducted a systematic first-principles investigation of N-doped alpha-Mo2C, focusing on its structural stability, electronic structure, phonon dynamics, and superconductivity. The results show that the superconductivity originates from the electron-phonon coupling (EPC) between Mo-4d orbital electrons and low-frequency vibrational modes of Mo atoms. As the N content increases, the Tc exhibits a dome-shaped variation, well-consistent with experimental observations. Notably, varying the N-doping concentration drives a Lifshitz transition and a trivial-nontrivial-trivial topological evolution, as confirmed by Wannier-based Z2 invariants. These findings provide important insights into the superconductivity and topology in N-doped alpha-Mo2C, and offer valuable guidance for the design of high-performance superconducting and topological quantum materials.

PdTe2 has been synthesized with controllable thickness down to the monolayer limit. Based on first-principles calculations within the fully anisotropic Migdal-Eliashberg framework, this work reveals that alkali-metal intercalation markedly enhances the weak superconductivity of bilayer PdTe2, boosting the transition temperature from 1.4 K to 5.0 -13.5 K and yielding a two-dome-like evolution of Tc. Rubidium intercalation induces the highest Tc of 13.5 K, which can be further increased to 14.5 K under biaxial tensile strain. The strain-dependent evolution of Tc also exhibits a two-dome-like behavior, reflecting the interplay between strain-induced band structure modifications and electron-phonon coupling (EPC). Moreover, a systematic correlation is identified between interlayer interaction and superconducting gap. Lithium intercalation induces a distinct two-gap state, whereas intercalants with larger atomic radii (Na, K, Rb, and Cs) drive the system into a single-gap character. The two-gap to single-gap transition originates from the modulation of interlayer coupling through intercalation-induced interlayer expansion. In addition, pristine and Li/Na-intercalated bilayers exhibit nontrivial band topology, suggesting that layered PdTe2 provides a promising platform for realizing the coexistence of superconductivity and nontrivial topology. These results provide detailed anisotropic insights into EPC and offer viable pathways for enhancing Tc and achieving diverse properties in layered PdTe2 systems.

Using first-principles calculations, we explore the electronic and topological properties of Janus VAZ3H single layers (A = Si, Ge; Z = N, P) that are dynamically and thermally stable. In the strain-free state, VSiN3H, VSiP3H, and VGeN3H demonstrate direct bandgap ferrovalley (FV) semiconducting properties, while VGeP3H displays an indirect bandgap. The easy magnetization axis varies among these materials, with VSiN3H and VGeN3H preferring in-plane magnetization, whereas VSiP3H and VGeP3H favor out-of-plane magnetization. Furthermore, the electronic structure analysis reveals valley polarization at the K and K' points. When subjected to strain, these systems experience phase transitions, such as direct-to-indirect bandgap shift, the evolution from FV semiconducting to half-valley metal (HVM), and the emergence of a quantum anomalous Hall (QAH) phase within certain strain intervals. The QAH phase is identified by chiral edge states and quantized anomalous Hall conductivity (AHC), supported by an integer AHC plateau of 1e2/h and a Chern number of 1. These results highlight the tunability of VAZ3H SLs through strain engineering, providing a potential platform for valleytronic and topological applications.

In recent years, the research on superconductivity in one-dimensional (1D) materials has been attracting increasing attention due to its potential applications in low-dimensional nanodevices. However, the critical temperature (Tc) of 1D superconductors is low. In this work, we theoretically investigate the possible high-Tc superconductivity of (5,5) carbon nanotube (CNT). The pristine (5,5) CNT is a Dirac semimetal and can be modulated into a semiconductor by full hydrogenation. Interestingly, by further hole doping, it can be regulated into a metallic state with the sp3-hybridized sigma electrons metalized, and a giant Kohn anomaly appears in the optical phonons. The two factors together enhance the electron-phonon coupling, and lead to high-Tc superconductivity. When the hole doping concentration of hydrogenated-(5,5) CNT is 2.5 hole/cell, the calculated Tc is 82.3 K, exceeding the boiling point of liquid nitrogen. Therefore, the predicted hole-doped hydrogenated-(5,5) CNT provides a new platform for 1D high-Tc superconductivity and may have potential applications in 1D nanodevices.

Recent experimental studies on the bilayer Ruddlesden-Popper phase nickelate La3Ni2O7 have shown that in the superconducting region, its superconducting transition temperature decreases monotonically from 83 K at 18 GPa as pressure further increases, exhibiting a nearly right-triangular temperature-pressure phase diagram that is different from the dome-shaped diagrams observed in cuprates and iron-based superconductors under either doping or pressure. It is important to understand this anomalous phase diagram in elucidating the superconducting mechanism of La3Ni2O7. Since the electron-phonon coupling mechanism cannot account for the high superconducting transition temperatures in nickelate superconductors, in this work, the pressure dependence of the transition temperature is investigated from the perspective of the itinerant electrons picture and the local spin picture. By combining the density functional theory (DFT) and the unbiased singular-mode functional renormalization group (SM-FRG) method, it is found that the pairing symmetry is consistently an s(+/-) -wave, driven by spin fluctuations that become progressively weakened under pressure, thereby decreasing in the superconducting transition temperature, which is in qualitative agreement with the experimental observation. On the other hand, we estimate that the pressure dependence in the local spin picture contradicts with the experimental result. Therefore, the pressure dependence of superconducting transition temperature is more consistent with the itinerant electrons picture. Admittedly, we only made a rough estimation based on the local spin picture. It is expected that further and more detailed research will be conducted on the pressure dependence of superconducting transition temperature from the local spin picture, providing deeper insights into the underlying superconducting mechanism of La3Ni2O7.

The coexistence and competition between the well-known quantum phenomena such as superconductivity, charge density wave (CDW), and band topology represent a cutting-edge frontier in the field of condensed matter physics. Two-dimensional (2D) Janus transition metal sulfide hydrides, a family of materials known for hosting diverse quantum phenomena, have drawn extensive attention recently. In this work, based on first- principles calculations, a novel member of this family, named 2H-MoSeH, is predicted. The pristine 2H-MoSeH exhibits CDW induced by electron-phonon coupling. Remarkably, this CDW state can be entirely suppressed under 2% biaxial compressive strain, giving rise to superconducting state with transition temperature (Tc) of 24 K. Moreover, CDW can also be suppresed by 0.15 hole doping per primitive cell, leading to superconductivity with a Tc of 17 K while simultaneously inducing a non-trivial band topology. The coexistence and tunable competition among superconductivity, CDW, and band topology in 2H-MoSeH establish it as an ideal platform for exploring novel quantum phenomena and designing new quantum devices.

Despite the numerous reports on the time-honored superconductor NiBi3, theoretical investigations remain limited, particularly regarding the impact of spin-orbit coupling (SOC). Based on first-principles calculations, the electronic topology of NiBi3 is mainly studied herein. Nodal loops which intersect to form a nodal chain structure are enclosed by two valence bands, and they are fully gapped by SOC. The full gap contains topological surface states defined by a Z2 topological invariant, while for the top valence band and bottom conduction band, a three-dimensional massless Dirac point at P is produced by the two bands with SOC. In addition, nodal surfaces which prevalently appear in the band structure without SOC are present on the entire Brillouin zone surface, and SOC only partially gaps them, thus leading to nodal lines unaffected by SOC. Type-I and type-II fermions, which are distinguished by the tilt of cones, are shown to coexist in the bulk bands. Furthermore, two Rashba-split bands are found on the (100) surface, whose inner and outer Fermi circles share the same spin polarization direction. Finally, our analysis reveals that the superconductivity of NiBi3 primarily originates from the p orbitals of Bi and d orbitals of Ni coupling with the vibration modes of Bi. The rich topological features identified in this study suggest that NiBi3 holds significant potential for realizations of topological superconductivity and other exotic phenomena.

Ferromagnetic materials play an important role in memory materials,but conventional control methods are often limited by issues such as high power consumption and volatility.Multiferroic heterostructures provide a promising alternative to achieve low power consumption and nonvolatile electric control of magnetic properties.In this paper,a two-dimensional multiferroic van der Waals heterostructure OsCl2/Sc2CO2,which is composed of ferromagnetic monolayer OsCl2 and ferroelectric monolayer Sc2CO2,is studied by first-principles density functional theory.The results show that by reversing the direction of the electric polarization of Sc2CO2,OsCl2 can be transformed from a semiconductor to a half-metal,demonstrating a nonvolatile electrical manipulation of the heterostructure through ferroelectric polarization.The underlying physical mechanism is explained by band alignments and charge density differences.Furthermore,based on the heterostructure,we construct a multiferroic tunnel junction with a tunnel electroresistance ratio of 3.38 × 1014％and a tunnel magnetoresistance ratio of 5.04 × 106％,allowing control of conduction states via instantaneous electric or magnetic fields.The findings provide a feasible strategy for designing advanced nanodevices based on the giant tunnel electroresistance and tunnel magnetoresistance effects.

Kagome lattice materials have attracted significant research interest due to their unique electronic structures and emergent quantum phenomena. Three-dimensional kagome systems have been extensively investigated, while the exploration of two-dimensional (2D) kagome materials remains relatively limited, presenting both scientific challenges and opportunities. In this work, through systematic first-principles calculations, MB6 (M = In, Tl), featuring in bilayer kagome borophene, are predicted to exhibit remarkable phonon-mediated superconductivity. These two compounds display superconducting transition temperatures (Tc) of 7.0 and 5.0 K, respectively, which are nearly two orders of magnitude higher than the 0.03 K predicted in intrinsic bilayer kagome borophene. Our analysis reveals that the coupling between B-pz, M-px/py (M = In, Tl) electrons and low-frequency phonons of metal atoms contributes greatly to their superconductivity. Notably, MB6 (M = In, Tl) possess nontrivial band topology, suggesting the potential candidates for topological superconductivity. This work not only expands the family of 2D superconducting materials, but also provides a theoretical exploration for novel quantum phenomena in kagome systems.

Pure borocarbides suffer from limited superconducting potential due to intrinsic structural instability, requiring transition/alkali metals as dual-functional stabilizers and dopants. Here, by combining high-throughput screening with anisotropic Migdal-Eliashberg (aME) theory, we identify dynamically stable borocarbides where high-Tc superconductivity predominately originates from E symmetry-selective electron-phonon coupling (EPC). The six distinct superconducting gaps emerge from a staircase distribution or uncoupling of EPC strength across each Fermi surface (FS) sheet, constituting a metal-free system with such high gap multiplicity. Crucially, dimensional reduction from bulk to surface strengthens E-symmetry EPC and enhances Tc from 32 K (3D bulk) to 75 K (2D surface), a result that highlights structural confinement as a key design strategy for observing high Tc. External strain further optimizes the competition between EPC strength and characteristic phonon frequency to achieve Tc > 90 K. This work reveals a systematic correlation between structural dimensionality and gap multiplicity and establishes borocarbide as a tunable platform to engineer both high-Tc and multi-gap superconductivity.

MXenes and MBenes, which are two-dimensional (2D) transition metal carbides/nitrides and borides, have been extensively studied for their impressive properties. Recently, we reported a family of transition metal sulfides MSene (M2S) with rich properties [Phys. Rev. B 111, L041404 (2025)], it is worth studying whether selenides with similar structure also have rich properties. In this work, through high-throughput screening, we present a novel family of 2D transition metal selenides, M2Se. In this family, there are fifty-eight candidate materials, of which ten are stable and metallic. Notably, eight exhibit superconductivity, among which four are superconducting topological metals. Besides, eight show charge density wave (CDW) behavior, among which five also exhibit antiferromagnetism. It is revealed that CDW originates from electron-phonon coupling rather than Fermi surface nesting. Moreover, strain can be applied to regulate the competition between CDW and superconductivity. Our findings reveal the rich properties of superconductivity, band topology, CDW, and magnetism in M2Se, providing a new platform for the controllable integration of multifunctional quantum states.