The Effects of Pressure on the Structural, Electronic, and Lattice Dynamical Properties of FeSe Superconductor

Abstract

Motivated by the experimental huge enhancement of the superconducting transition temperature T c in FeSe superconductor under high pressure, we perform first-principles calculations of the evolutions of structural, electronic, and lattice dynamical properties of FeSe at varying hydrostatic pressures up to 8 GPa. The pressure response is anisotropic with a larger compressibility along c-axis. At ambient pressure, Fermi surface nesting between hole and electron pockets induces spin density wave (SDW) order at the vector (π , π , 0) with a collinear antiferromagnetic structure. With the increase of pressure, the Fermi surface nesting is reduced, and therefore the SDW is suppressed, which could not enhance superconductivity based on the spin-fluctuation scenario. For the phonon dispersion, the bands have blue-shift except for the modes around 100 cm −1 , indicating hardening of the vibration modes in a wide frequency range. Furthermore, the electron-phonon coupling constant and the corresponding T c by McMillan equation are calculated. However, there is no obvious enhancement of T c under pressure, which further rules out the conventional phonon-mediated superconductivity of FeSe. Maybe the local magnetic moment plays an important role for the superconductivity and enhancement of T c under pressure.

Novel electronic and phonon-related properties of the newly discovered silicide superconductor Li 2 IrSi 3

“…2(a), the obvious dispersions along Γ-A, H-K, and M -L lines show a three-dimensional (3D) character of the band structure, indicating distinct interlayer hybridization. This is very different from the well-known 2D band structure in layered cuprates [19] and iron-based superconductors [20,25], which show weak interlayer interactions. There are two bands crossing the Fermi energy, which are denoted by red and blue lines.…”

Superconducting Properties of F e S e 0.5 T e 0.5 Under High Pressure

“…On the other hand, the dependence of superconducting properties with pressure of this compound implying that microscopic mechanism of the electronic pairing is different of electron-phonon, as it is shown in unconventional superconductors. Other reports on similar studies [39,40], indicate that the increment of the density of electronic states are not enough to explanation the notable increment of the transition temperature. The presence of a Peierls distortion, as a Spin Density Wave, must be decreased by pressure but nevertheless has any influence on the transition temperature, again this is quite anomalous.…”

Pressure effects on the FeSe-based superconductors

“…高压调控在FeSe基超导体的研究中发挥了重要 的推动作用 [27][28][29][30][31][32][33][34][35] . 在2008年发现FeSe超导之后, 人们首 先对其超导性质开展了高压调控研究, 发现其T c 在 高压下快速升高 [36] , 8-10 GPa时可以达到最高T c ≈ 37 K [37][38][39][40][41] , 使其进入高温超导体行列.…”