K-Doping Dependence of the Fermi Surface of the Iron-ArsenicBa1−xKxFe2As2Superconductor Using Angle-Resolved Photoemission Spectrosc

Abstract

We use angle-resolved photoemission spectroscopy (ARPES) to investigate the electronic properties of the newly discovered iron-arsenic superconductor, Ba1−xKxFe2As2 and non-supercondcuting BaFe2As2. Our study indicates that the Fermi surface of the undoped, parent compound BaFe2As2 consists of hole pocket(s) at Γ (0,0) and larger electron pocket(s) at X (1,0), in general agreement with full-potential linearized plane wave (FLAPW) calculations. Upon doping with potassium, the hole pocket expands and the electron pocket becomes smaller with its bottom approaching the chemical potential. Such an evolution of the Fermi surface is consistent with hole doping within a rigid band shift model. Our results also indicate that FLAPW calculation is a reasonable approach for modeling the electronic properties of both undoped and K-doped iron arsenites.PACS numbers: 74.25.Jb, Iron-Arsenic based materials comprise a very interesting class of materials with many unusual properties. For example, they have recently been shown to be superconducting with a T c as high as 55K [1,2,3]. This discovery has initiated a frenzy of research activity, which until very recently was limited to studies of only polycrystalline samples. Initial experiments focused on fluorine-doped rare earth oxide based materials (RFeAsOF) [4,5,6]. To date, there is very little photoemission data available on these compounds [7,8,9] with only one angle resolved study [10]. The recent discovery of superconductivity in oxygen free Ba 1−x K x Fe 2 As 2 [11] suggests that the superconductivity is ultimately linked to the electronic properties of the iron arsenic layer(s) with the remaining layers acting as a charge reservoir. This scheme closely resembles the situation found in the cuprates but without oxygen. In both BaFe 2 As 2 and SrFe 2 As 2 there are clear structural phase transitions from a high temperature tetragonal to low temperature orthorhombic phases. [12,13] When potassium is substituted for barium, the temperature at which the structural transition occurs is suppressed and superconductivity emerges [11,12]. Some experiments also point to the existence of a transition into a spin density wave (SDW) state at higher temperature [5,14] and related changes of the electronic structure [15]. Determining the effects of doping on low lying electronic excitations is essential for this study, as they play significant role in determining the normal state and superconducting properties. It is equally important to understand the electronic properties of the parent compound because undoped systems are easier to model theoretically and they represent a basis for higher order approximations. The information about electronic structure and its evolution with doping is deemed essential to formulate a successful model of superconductivity in these fascinating systems.The recent growth of large, high quality single crystals [12] has opened up the possibility of examining the electronic properties of these materials. Here we present data from angle resolved photoemission s...

Magnetically driven suppression of nematic order in an iron-based superconductor

“…In such an electronic structure, interactions between electrons near the two sets of pockets give rise to a spin density wave (SDW) order at the wave vector connecting them 8 . This itinerant picture is consistent with the wave vector of the observed antiferromagnetism, angle resolved photoemission (ARPES) measurements of the electronic structure 9,10 and the evolution of the dynamic magnetic susceptibility with carrier concentration [11][12][13] .…”

Three-dimensionality of band structure and a large residual quasiparticle population in Ba0.67K0.33<

“…Presence of 3D Fermi surfaces (FSs) was also suggested from band structure calculations 22 and a number of other experimental probes. [23][24][25][26][27] In particular, recent ab-initio LDA+Gutzwiller calculations, where electron correlations are taken into account beyond LDA, indicated that the large-size 3D ellipsoid like FS has a dominant Fe-3d 3z 2 −r 2 orbital characteristic 22 . Then the key issue is to understand why an s-wave superconducing energy gap is clearly seen from the in-plane optical measurement, whereas a large residual quasiparticle population is indicated in the c-axis polarized optical measurement.…”

Electronic properties of novel 6 K superconductor LiFeP in comparison with LiFeAs from first principles calculations

“…Thus, the results obtained reveal that various atomic replacements inside "122" phases can lead to essential anisotropic changes of their structural properties and are favorable for fine tuning of their geometry -in particular, in view of sensitivity of superconductivity to structural changes, see [31,32].…”