Regensburg 2022 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 12: Correlated Electrons: Materials
TT 12.12: Vortrag
Dienstag, 6. September 2022, 12:30–12:45, H22
Orbital order and nematic instability in the antiferromagnetic phase of BaCoS2 — •Benjamin Lenz1, Michele Fabrizio2, and Michele Casula1 — 1Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Sorbonne University - CNRS - MNHN, Paris, France — 2Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste, Italy
We present evidence for a nematic instability in the antiferromagnetic insulating phase of BaCoS2, which shows a Néel transition at a surprisingly high temperature of TN∼300K. Based on ab initio simulations, we discuss several competing orders in terms of magnetic order, orbital composition and structural distortions to identify a set of nematic and orbital ordered states as possible candidates for the ground state. From these considerations we derive an effective spin-model of J1−J2 type and discuss the consequences of the most probable, orbital ordered ground state for its parametrization. We finally identify a driving mechanism which allows to explain the high Néel temperature by C4-symmetry breaking through orbital order and draw parallels to other quasi-2D materials such as pnictides.