Electronic structure, topological phase transitions and superconductivity in (K, Cs) x Fe2Se2

Electronic structure of new iron-based superconductors: From pnictides to chalcogenides and other similar systems

“…10 shows Fermi surfaces for SrPt 3 P (left) and LaPt 3 P (right) obtained by us via LDA calculations. In general, the form of Fermi surface of APt 3 P systems sharply differs from those in iron pnictides and chalcogenides [24,27]. In particular, these Fermi surfaces are essentially of three-dimensional nature and do not have well-defined cylinders.…”

“…1 we compare band structures and densities of states of Ba122 [24] (left) with corresponding calculation results for K 1−x Fe 2 Se 2 (black lines) and Cs 1−x Fe 2 Se 2 (gray lines) (right) for stoichiometric compositions with x=0 [27]. Comparing K 1−x Fe 2 Se 2 and Cs 1−x Fe 2 Se 2 systems we can note, that both have practically identical electronic structures.…”

“…This short review is based upon the cycle of our investigations of electronic structure of all these systems within the framework of density functional theory and modern methods to take into account strong correlations, like LDA+DMFT [14] and LDA ′ +DMFT [15,16] for iron chalcogenides [17,18], as well as upon the results of LDA calculations for above mentioned similar systems [19,20,21,22]. These works were preceded by rather long series of our works on iron pnictides and chalcogenides [23,24,25,26,27], the results of these works were discussed in details in our previous reviews [2,5] All LDA calculations of band structures presented below were performed using the basis of linearized muffin-tin orbitals (LMTO) [28], with default parameters.…”

Cesium vacancy ordering in phase-separatedCsxFe2−ySe2Taddei1, Sturza2, Chung3 et al. 2015Phys. Rev. B9360View full textAdd to dashboardCite

“…Though isostructural to the pnictide family at high temperatures, the iron selenides show striking differences: they have a Fermi surface morphology devoid of the Γ hole pocket thought to be vital to the superconducting pairing in the pnictides, a strong AFM ordering with T N more than twice that of the iron pnictides and a large magnetic moment that would appear to indicate a Mott Insulator, in addition they also exhibit two distinct coexisting phases, with radically different properties. [14,15,16,17] Phase separation in the intercalated iron selenides is well-established and this induction of microscopic domains of minority 122-type structure in a host matrix with robust magnetic properties is unique and interesting. [17,18,19,20,21,22] Though its formation is widely reported, the exact nature of this minority phase remains debated, being described as isostructural with the higher temperature paramagnetic 122 phase from x-ray diffraction on polycrystalline K x Fe 2-y Se 2 or as being distorted to lower orthorhombic or monoclinic symmetries as found in x-ray diffraction on Rb x Fe 2-y Se 2 and Cs x Fe 2-y Se 2 single crystals, respectively.…”

Elastic properties and inter-atomic bonding in new superconductor from first principles calculations

“…So, the attention was paid to the transport properties of new 122-like FeSe phases [1][2][3][4][5][6][7]. The intense researches of their electronic band structure and magnetic ordering [8][9][10][11][12][13], of the effects of pressure [14][15][16] and non-stoichiometry [1][2][3][4][5][6][7][11][12][13][14][15][16] and so on are carried out now.…”