We demonstrate, using T=0 first principles total energy calculations, that observed pressure-driven anomalies in the entire 122-pnictides family (AFe2As2; A = alkali earth element Ca, Sr, Ba) can be understood as consequences of Lifshitz transitions (LTs) \cite{Lifshitz60}. Our results for energy band dispersions and spectra, lattice parameters, enthalpies, magnetism, and elastic constants over a wide range of hydrostatic pressure provide a coherent understanding of multiple transitions in these compounds, namely, enthalpic, magnetic and tetragonal (T) - collapsed tetragonal (cT) transitions. In particular, the T-cT transition and anomalies in lattice parameters and elastic properties, observed at finite temperatures, are interpreted as arising from proximity to T=0 Lifshitz transitions, wherein pressure causes non-trivial changes in the Fermi surface topology in these materials.
@article{arxiv.1401.7349,
title = {Lifshitz Transitions in 122-Pnictides Under Pressure},
author = {Khandker Quader and Michael Widom},
journal= {arXiv preprint arXiv:1401.7349},
year = {2015}
}