Superconductivity in two-dimensional compounds is widely concerned, not only due to its application constructing nano-superconducting devices, but also for the general scientific interests. Very recently, borophene (two-dimensional boron sheet) has been successfully grown on Ag(111) surface, through direct evaporation of a pure source. The experiment unveiled two types structures, namely $\beta_{12}$ and $\chi_3$. Herein, we employed density-functional first-principles calculations...

We studied the pairing instabilities in KxFe2−ySe2 using a two-stage functional renormalization group (FRG) method. Our results suggest leading and subleading symmetries are nodeless dx2−y2 nodal extended s, respectively. In addition, despite having no Fermi surfaces we find buried hole bands make important contributions to final effective interaction. From bandstructure, spin susceptibility FRG conclude that low-energy interaction is well described by J1-J2 model with dominant...

Discovery of high-temperature superconductivity in hydrogen-rich compounds has fuelled the enthusiasm for finding materials with more promising superconducting properties among hydrides. However, ultrahigh pressure needed to synthesize and maintain superconductors hinders experimental investigation these materials. For practical applications, it is also highly desired find that superconduct at high temperatures but under relatively lower pressures. Based on first-principles density...

An experimental study found superconductivity in bilayer phase of La3Ni2O7, with the highest superconducting transition temperature (Tc) ∼ 80 K under pressure. Recently, some reports claimed that there exists a competitive monolayer-trilayer structural La3Ni2O7 compounds. We perform first-principles calculations and find is energetically favorable Although extensive studies have been done to investigate electronic correlation potential pairing mechanism phonon properties electron-phonon...

By the first-principles electronic structure calculations, we find that ground state of Fe-vacancies ordered TlFe(1.5)Se(2) is a quasi-two-dimensional collinear antiferromagnetic semiconductor with an energy gap 94 meV, in agreement experimental measurements. This order driven by Se-bridged superexchange interactions between Fe moments. Similarly, crystals AFe(1.5)Se(2) (A=K, Rb, or Cs) are also semiconductors but zero-gap semiconducting semimetallic nearly degenerated states. Thus, rich...

We have studied electronic and magnetic structures of K$_{0.8+x}$Fe$_{1.6}$Se$_2$ by performing the first-principles structure calculations. The ground state Fe-vacancies ordered K$_{0.8}$Fe$_{1.6}$Se$_2$ is found to be a quasi-two-dimensional blocked checkerboard antiferromagnetic (AFM) semiconductor with an energy gap 594 meV large ordering moment 3.37 $\mu_B$ for each Fe atom, in excellent agreement neutron scattering measurement. underlying mechanism chemical-bonding-driven tetramer...

We report a thorough study of the transport properties normal and superconducting states black phosphorus (BP) under magnetic field high pressure with large-volume apparatus that provides hydrostatic to induce transitions from layered A17 phase A7 cubic BP. Quantum oscillations can be observed at

Applying pressure around megabar is indispensable in the synthesis of high-temperature superconducting hydrides, such as SH$_3$ and LaH$_{10}$. Stabilizing high-pressure phase hydride ambient condition a severe challenge. Based on density-functional theory calculations, we give first example that structure CaBH$_5$ predicted above 280 GPa, can maintain its dynamical stability with down to 1 by modulating charge transfer from metal atoms hydrogen via replacement Ca alkali e.g. Cs, which...

Based on the first-principles density functional theory calculations for electronic band structure and lattice dynamics of ${\mathrm{Li}}_{3}{\mathrm{B}}_{4}{\mathrm{C}}_{2}$, we predict that this material is a strong electron-phonon coupled superconductor with superconducting transition temperature higher than ${\mathrm{MgB}}_{2}$. ${\mathrm{Li}}_{3}{\mathrm{B}}_{4}{\mathrm{C}}_{2}$ layered which formed by substituting one-third carbon atoms in semiconducting compound LiBC boron atoms,...

Very recently, carbon-boron clathrate $\mathrm{Sr}{\mathrm{B}}_{3}{\mathrm{C}}_{3}$ has been successfully synthesized, in which carbon and boron atoms form $s{p}^{3}$-bonded truncated octahedral cages. Interestingly, the $s{p}^{3}$-hybridized $\ensuremath{\sigma}$-bonding bands are partially occupied. This may drive into a superconducting state, like boron-doped diamond. By means of density functional first-principles calculations Wannier interpolation technique, we have investigated...

To design a phonon-mediated superconductor with transition temperature above the liquid-nitrogen under ambient pressure, we align Fermi level of compound ${\mathrm{SrB}}_{3}{\mathrm{C}}_{3}$ to Van Hove singularity by introducing 0.4 hole/f.u., namely ${\mathrm{Rb}}_{0.4}{\mathrm{Sr}}_{0.6}{\mathrm{B}}_{3}{\mathrm{C}}_{3}$. Based on density functional first-principles calculations and Wannier interpolation technique, electronic structure, lattice dynamics, electron-phonon coupling (EPC)...

We have studied the electronic and magnetic structures of ternary iron selenides $A$Fe${}_{2}$Se${}_{2}$ ($A$ $=$ Cs, Rb, K, or Tl) using first-principles structure calculations. find that ground state these compounds is bicollinearly antiferromagnetically ordered, with Fe moments having collinear antiferromagnetic order in each bipartite sublattice. This bicollinear results from superexchange interactions mediated by Se $4p$ orbitals. also determined density states at Fermi level, specific...

Coupling between $\sigma$-bonding electrons and phonons is generally very strong. To metallize $\sigma$-electrons provides a promising route to hunt for new high-T$_c$ superconductors. Based on this picture first-principles density functional calculation with Wannier interpolation electronic structure lattice dynamics, we predict that trilayer film LiB$_2$C$_2$ good candidate realize kind of superconductivity. By solving the anisotropic Eliashberg equations, find free-standing...

A recent experimental study announced the emergence of superconductivity in La$_3$Ni$_2$O$_7$ under pressure, with highest observed superconducting transition temperature ($T_c$) reaching approximately 80 K beyond 14 GPa. While extensive studies have been devoted to electronic correlations and potential pairing mechanisms, there lack investigations into phonon properties electron coupling. Using density functional theory conjunction Wannier interpolation techniques, we interactions 29.5 Our...

Binary transition metal nitride with a graphene-like structure and strong magnetic properties is rare. Based on the first-principles calculations, we design two kinds of $M{\mathrm{N}}_{4}$ ($M$ = metal) monolayers, which are nitrides planar structure, made up units aligned in rhombic square patterns. The structural lattices have robust stability good compatibility different atoms, underlying mechanism combination $s{p}^{2}$ hybridization, coordinate bond, $\ensuremath{\pi}$ conjugation....

By the first-principles electronic structure calculations, we find that energetically most favorable cleaved $A$Fe$_2$As$_2$(001) surface ($A$=Ba, Sr, or Ca) is $A$-terminated with a $(\sqrt{2}\times \sqrt{2})R45^{\circ}$ $(1\times 2)$ order. The ordered yields dimerized STM image, in agreement experimental observation. $A$ atoms are found to diffuse on small energy barrier so cleaving process may destroy ordering. At very low temperatures this result an As-terminated randomly assembling....

Recently, a honeycomb borophene was reported to grow successfully on Al(111) surface. Since the metallic $\sigma$-bonding bands of boron sheet play crucial role in 39 K superconductivity MgB$_2$, it is physically interesting examine whether similar property exists this material. We have calculated electronic structures and electron-phonon coupling for by explicitly considering substrate effect using first-principles density functional theory conjunction with Wannier interpolation technique....

Based on density-functional first-principles calculations and the Wannier interpolation technique, we have investigated electron-phonon coupling (EPC) in hole-doped monolayer hexagonal boron nitride (h-BN). We align Fermi level to a Van Hove singularity by 0.4 holes/cell doping, largest hole concentration that can be realized h-BN. Under this doping level, EPC for free-standing h-BN is weak. However, biaxial tensile strain enhance significantly. predict become phonon-mediated superconductor...

The recent report of superconductivity in the Cu-doped PbPO compound stimulates extensive researches on its physical properties. Herein, detailed atomic and electronic structures this are investigated, which necessary information to explain properties, including possible superconductivity. By first-principles structure calculations, we find that partial replacement Pb at $4f$ site by Cu atom, instead $6h$ site, plays a crucial role dominating state Fermi energy. $3d$ orbitals atom emerge...

A topological superconductor candidate $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{RhPb}}_{2}$ is predicted by using first-principles electronic structure calculations. Our calculations show that there a band inversion around the Fermi level at $Z$ point of Brillouin zone. The calculated nonzero invariant ${\mathrm{Z}}_{2}$ indicates insulator defined on curved level. Slab further demonstrate gapless nontrivial surface states (TSS) are not overlapped bulk and they cross Phonon confirm...

Based on the first-principles simulations within framework of density functional theory, we predict that ${\mathrm{CoN}}_{4}{\mathrm{C}}_{2}$ is a single-atom-thick two-dimensional material, which composed ${\mathrm{CoN}}_{4}$ unit and ${\mathrm{C}}_{2}$ dimer. The cohesive energy phonon dispersion calculations monolayer, as well molecular dynamics simulation, have been carried out its stability confirmed. electronic states near Fermi are dominated by Co $3d$ orbital $2p$ orbitals C N atoms...

The design and exploration of ferromagnetic two-dimensional materials is an important research topic due to their potential applications in spintronic devices. By the first-principles calculations, we examine structural stability electronic properties transition metal carbonitrides MN4C2 (M = 3d metals) find out that chromium carbonitride CrN4C2 a material. made up CrN4 unit C2 dimer, stacked alternatively form planar single-atom-thick sheet. For Cr states, there complete spin splitting...

Based on the first-principles density functional theory electronic structure calculation, we investigate possible phonon-mediated superconductivity in arsenene, a two-dimensional buckled arsenic atomic sheet, under electron doping. We find that strong superconducting pairing interaction results mainly from $p_z$-like electrons of atoms and $A_1$ phonon mode around $K$ point, transition temperature can be as high 30.8 K arsenene with 0.2 doped per unit cell 12\% applied biaxial tensile...

We use neutron scattering to study the spin excitations associated with stripe antiferromagnetic order in semiconducting ${\mathrm{K}}_{0.85}{\mathrm{Fe}}_{1.54}{\mathrm{Se}}_{2}$ (${T}_{N}=280\text{ }\text{ }\mathrm{K}$). show that spin-wave spectra can be accurately described by an effective Heisenberg Hamiltonian highly anisotropic inplane couplings at $T=5\text{ }\mathrm{K}$. At high temperature ($T=300\text{ }\mathrm{K}$) above ${T}_{N}$, short-range magnetic correlation lengths are...