Electronic structure and phonon spectrum of binary iron-based superconductor FeSe in both nonmagnetic and striped antiferromagnetic phases

Using first-principles calculations, we investigate electronic structure and phonon spectrum of binary iron-based superconductor FeSe in both tetragonal nonmagnetic (NM) phase and orthorhombic striped antiferromagnetic (SAF) phase. It is found that the softening of atomic vibration modes and main electron–phonon coupling contribution from low-frequency Eliashberg spectral function α2F(ω)α2F(ω) in SAF phase of FeSe lead to the enhancement of electron–phonon coupling strength λepλep and logarithmically average frequency ωlnωln. However, the obtained superconducting TcTc in SAF phase just increases up to 0.34 K, even though Coulomb pseudopotential μ∗μ∗ is limited to zero. As a result, our magnetic phonons calculation still rules out phonon mediated superconductivity, although the electron–phonon coupling through the spin channel play an important role in FeSe.

► Phonon softening in orthorhombic striped antiferromagnetic phase of FeSe.
► A large frequency gap exists in orthorhombic striped antiferromagnetic phase of FeSe.
► Magnetic phonons are still not responsible for superconductivity of FeSe.