Motivated by growing indications for a distinct form of nematic correlations in the extremely hole doped iron pnictide compounds AFe2As2 (A=K,Rb,Cs), we consider spin-driven nematic order in the general case of incommensurate magnetic fluctuations. We classify the nematic order parameters by broken mirror symmetries of the tetragonal D4h point group, and use this scheme to construct a general Ginzburg-Landau theory that links the nematic order to spatial pattern of magnetic fluctuations. Our analysis points to incommensurate magnetic fluctuations of wavevector (q,q) as underlying a B2g nematic order in AFe2As2. We substantiate this idea by microscopic calculations of the nematic order based on 3-sublattice (2π/3,2π/3) spin correlations in an extended bilinear-biquadratic Heisenberg model. We summarize the existing evidence in support of the proposed mechanism, suggest ways to further test it in future experiments, and discuss the implications of our results for iron-based high temperature superconductivity.
@article{arxiv.1903.00375,
title = {Broken mirror symmetry, incommensurate spin correlations, and $B_{2g}$ nematic order in iron pnictides},
author = {Yiming Wang and Wenjun Hu and Rong Yu and Qimiao Si},
journal= {arXiv preprint arXiv:1903.00375},
year = {2019}
}