| Superconductivity in metal borides has been extensively studied for decades.Especially,since the discovery of 39 K superconductivity in MgB2,whether other metal borides can superconduct at a relatively high transition temperature is widely concerned.We used the first-principles calculation based on the density-functional theory and Wannier interpolation to study whether the superconducting mechanism of FeB4 is electron-phonon coupling,and the possible superconductivity in CuB4 that isomorphic with FeB4.In addition to iron arsenides and iron selenides,FeB4 is another iron-based superconductor,whose superconducting transition temperature Tc is 2.9 K.Despite the relatively lower Tc in FeB4 with respect to the common iron-based superconductors,the existing theoretical works on the superconductivity in FeB4 with phonon-mediated mechanism are still controversial.In our study,the electron-phonon coupling in FeB4 is accurately determined by means of first-principles electronic structure calculation and Wannier interpolation.We find that the electron-phonon coupling constant?for FeB4 is 1.41,which can give rise to 50 K superconductivity by utilizing the McMillian-Allen-Dynes formula.Our accurate calculations unambiguously clarify that FeB4 is not an ordinary phonon-mediated superconductor.We further explore whether there are materials with strong electron-phonon coupling and relatively weak ferromagnetic fluctuation in the transition metal tetrabororide.So,we have studied the electronic structure,lattice dynamic,and electron-phonon coupling?EPC?in CuB4and ZnB4,whose crystal structure is formed by directly substituting Cu?Zn?for Fe in FeB4lattice.As revealed by the calculated phonon spectrum,CuB4 is dynamically stable.It is found that the EPC constant?is 0.55 for CuB4,which can give rising to a Tc of 7.6 K by solving the isotropic Eliashberg equations.Our prediction makes CuB4 as a phonon-mediated superconductor,with relatively high Tc among binary metal borides. |
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