Ab initio perspective on structural and electronic properties of iron‐based superconductors

Abstract

The discovery of iron pnictides and iron chalcogenides as a new class of unconventional superconductors in 2008 has generated an enormous amount of experimental and theoretical work that identifies these materials as correlated metals with multi‐orbital physics, where magnetism, nematicity, and superconductivity are competing phases that appear as a function of pressure and doping. A microscopic understanding of the appearance of these phases is crucial in order to determine the nature of superconductivity in these systems. Here, we review our recent theoretical efforts to describe and understand from first principles the properties of iron pnictides and chalcogenides with special focus on (i) pressure dependence, (ii) effects of electronic correlation, and (iii) origin of magnetism and superconductivity.

Constraints on the total coupling strengthto bosons in the iron based superconductors

“…For example, an orbital ‐resolved ARPES analysis for the undoped LiFeAs and the el ‐doped Ba() 2 As 2 results in comparable numbers for the band renormalization renormalization: about 2.3 and 2.1 for the el ‐pockets with 3 and 3 character in Ba‐122 and 2.2 (1.8) for the el (h)’pockets with 3 character, but 4 (3.3) for the el (h)’pockets of 3 character in LiFeAs. The increased values of the former are in accord with the DMFT predictions for the importance of correlation effects for the 3 states with further h ‐doping .…”

Microscopic Modeling of Correlated Systems Under Pressure: Representative Examples

“…it is possible to steer the systems through various phase transitions in a controlled way. As a matter of fact, this technique has proven to be utterly useful to uncover the nature of quantum phases, such as a Mott insulator, spin liquid, correlated metal, multiferroic, or unconventional superconductor . Materials where such a tuning parameter is very effective are, for instance, organic charge transfer salts, where, due to the softness of the organic components, small pressures induce large changes in the electronic properties of the materials giving rise to complex phase diagrams .…”

“…As a matter of fact, this technique has proven to be utterly useful to uncover the nature of quantum phases, such as a Mott insulator, spin liquid, [1][2][3][4][5][6][7][8][9][10][11][12] correlated metal, multiferroic, [13][14][15][16][17][18][19][20] or unconventional superconductor. [21][22][23][24][25][26][27][28][29][30][31][32][33] Materials where such a tuning parameter is very effective are, for instance, organic charge transfer salts, where, due to the softness of the organic components, small pressures induce large changes in the electronic properties of the materials [13][14][15][16][17][18][19][20] giving rise to complex phase diagrams. [34][35][36] Also inorganic materials can show extreme sensitivity to pressure due to formation and breaking of certain covalent bonds in their crystal structures upon pressurizing.…”

Nontrivial Role of Interlayer Cation States in Iron-Based Superconductors

“…Magnetism plays an important role in superconductivity of Fe-based superconductors (FeBS) [2,[18][19][20][21][22][23][24]. It is therefore natural to ask whether the magnetic tendencies in iron germanides are fundamentally different from those in iron pnictides and chalcogenides [25] and why that is the case.…”