M Smoluchowski Institute of Physics, Jagiellonian University, Kraków, Poland.
J Phys Condens Matter. 2013 May 15;25(19):195701. doi: 10.1088/0953-8984/25/19/195701. Epub 2013 Apr 19.
The electronic structure of superconducting Fe1.03Te0.94S0.06 has been studied by angle-resolved photoemission spectroscopy (ARPES). Experimental band topography is compared to the calculations using the methods of Korringa-Kohn-Rostoker (KKR) with the coherent potential approximation (CPA) and the linearized augmented plane wave with local orbitals (LAPW+LO) method. The region of the Γ point exhibits two hole pockets and a quasiparticle peak close to the chemical potential (μ) with undetectable dispersion. This flat band with mainly d(z)(2) orbital character is most likely formed by the top of the outer hole pocket or is evidence of a third hole band. It may cover up to 3% of the Brillouin zone volume and should give rise to a Van Hove singularity. Studies performed for various photon energies indicate that at least one of the hole pockets has a two-dimensional character. The apparently nondispersing peak at μ is clearly visible for 40 eV and higher photon energies, due to an effect of the photoionization cross-section rather than band dimensionality. Orbital characters calculated by LAPW+LO for stoichiometric FeTe do not reveal the flat dz(2) band but are in agreement with the experiment for the other dispersions around Γ in Fe1.03Te0.94S0.06.
用角分辨光电子能谱（ARPES）研究了超导 Fe1.03Te0.94S0.06 的电子结构。实验能带形貌与使用 Korringa-Kohn-Rostoker（KKR）方法与相干势近似（CPA）和线性化增强平面波与局域轨道（LAPW+LO）方法的计算进行了比较。Γ 点区域表现出两个空穴口袋和一个准粒子峰接近化学势（μ），没有可检测的色散。这个主要由 d(z)(2)轨道特性组成的扁平带很可能是由外空穴口袋的顶部形成的，或者是第三个空穴带的证据。它可能占据布里渊区体积的 3%，应该会产生范霍夫奇点。对各种光子能量进行的研究表明，至少有一个空穴口袋具有二维特性。由于光离化截面而不是带维数的影响，μ 处明显不色散的峰在 40 eV 及更高的光子能量下清晰可见。由 LAPW+LO 计算出的轨道特性对于化学计量的 FeTe 并没有揭示出扁平的 dz(2)带，但与 Fe1.03Te0.94S0.06 中Γ 周围其他色散的实验结果一致。
