Phase stability and large in-plane resistivity in the 112-type iron-based superconductor Ca$_{1-x}$La$_{x}$FeAs$_{2}$

Chang-Jong Kang; Turan Birol; Gabriel Kotliar

doi:10.1103/PhysRevB.95.014511

paper

Phase stability and large in-plane resistivity in the 112-type iron-based superconductor Ca $_{1 - x}$ La $_{x}$ FeAs $_{2}$

arXiv:1612.06964 · doi:10.1103/PhysRevB.95.014511

Abstract

The recently discovered high-T $_{c}$ superconductor Ca $_{1 - x}$ La $_{x}$ FeAs $_{2}$ is a unique compound not only because of its low symmetry crystal structure, but also because of its electronic structure which hosts Dirac-like metallic bands resulting from (spacer) zig-zag As chains. We present a comprehensive first principles theoretical study of the electronic and crystal structures of Ca $_{1 - x}$ La $_{x}$ FeAs $_{2}$ . After discussing the connection between the crystal structure of the 112 family, which Ca $_{1 - x}$ La $_{x}$ FeAs $_{2}$ is a member of, with the other known structures of Fe pnictide superconductors, we check the thermodynamic phase stability of CaFeAs $_{2}$ , and similar hyphothetical compounds SrFeAs $_{2}$ and BaFeAs $_{2}$ which, we find, are slightly higher in energy. We calculate the optical conductivity of Ca $_{1 - x}$ La $_{x}$ FeAs $_{2}$ using the DFT + DMFT method, and predict a large in-plane resistivity anisotropy in the normal phase, which does not originate from electronic nematicity, but is enhanced by the electronic correlations. In particular, we predict a 0.34 eV peak in the $y y$ component of the optical conductivity of the 30\% La doped compound, which correponds to coherent interband transitions within a fast-dispersing band arising from the zig-zag As-chains which are unique to this compound. We also study the Landau free energy for Ca $_{1 - x}$ La $_{x}$ FeAs $_{2}$ including the order parameter relevant for the nematic transition and find that the free energy does not have any extra terms that could induce ferro-orbital order. This explains why the presence of As chains does not broaden the nematic transition in Ca $_{1 - x}$ La $_{x}$ FeAs $_{2}$ .

14 pages, 14 figures

Phase stability and large in-plane resistivity in the 112-type iron-based superconductor Ca $_{1 - x}$ La $_{x}$ FeAs $_{2}$

Abstract

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Phase stability and large in-plane resistivity in the 112-type iron-based superconductor Ca1−x​Lax​FeAs2​

Abstract

References in corpus (14)

Cited by in corpus (2)

Phase stability and large in-plane resistivity in the 112-type iron-based superconductor Ca $_{1 - x}$ La $_{x}$ FeAs $_{2}$