Preemptive nematic order, pseudogap, and orbital order in the iron pnictides

R. M. Fernandes, A. V. Chubukov, J. Knolle, I. Eremin, J. Schmalian

Research output: Contribution to journalArticlepeer-review

317 Scopus citations


Starting from a microscopic itinerant model, we derive and analyze the effective low-energy model for collective magnetic excitations in the iron pnictides. We show that the stripe magnetic order is generally preempted by an Ising-nematic order, which breaks C 4 lattice symmetry but preserves O(3) spin-rotational symmetry. This leads to a rich phase diagram as function of doping, pressure, and elastic moduli, displaying split magnetic and nematic tricritical points. The nematic transition may instantly bring the system to the verge of a magnetic transition, or it may occur first, being followed by a magnetic transition at a lower temperature. In the latter case, the preemptive nematic transition is accompanied by either a jump or a rapid increase of the magnetic correlation length, triggering a pseudogap behavior associated with magnetic precursors. Furthermore, due to the distinct orbital character of each Fermi pocket, the nematic transition also induces orbital order. We compare our results to various experiments, showing that they correctly address the changes in the character of the magnetostructural transition across the phase diagrams of different compounds, as well as the relationship between the orthorhombic and magnetic order parameters.

Original languageEnglish (US)
Article number024534
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number2
StatePublished - Jan 25 2012


Dive into the research topics of 'Preemptive nematic order, pseudogap, and orbital order in the iron pnictides'. Together they form a unique fingerprint.

Cite this