Orbital ordering in the iron-ladder material BaFe2S3 studied by elastoresistance measurements

BaFe₂S₃ is one of the most attractive materials in that superconductivity appears in the vicinity of bandwidth-control type Mott transition under high pressure. At ambient pressure, BaFe₂S₃ is a semiconductor with antiferromagnetic ordering at T_N ~ 110 K and another transition at around T* ~ 200 K characterized by a small anomaly in resistivity. One of the speculations is that orbital degrees of freedoms play an important role in this unidentified transition, and there is a suggestion of a possible orbital order similar to the nematic order in iron-based superconductors with Fe square lattice. Elastoresistance under uniaxial strain is a powerful tool to elucidate the nature of orbital ordering through the evaluation of its nematic fluctuations. Here we apply this elastoresistance technique to BaFe₂S₃ and investigate temperature dependence of putative orbital fluctuations. Our elastoresistance measurements reveal a clear anomaly at T* consistent with resistivity measurements, indicating the presence of electronic phase transition.