Ergueta, Patricia BilbaoHu, Wen-JunNevidomskyy, Andriy H.2018-01-232018-01-232017Ergueta, Patricia Bilbao, Hu, Wen-Jun and Nevidomskyy, Andriy H.. "Unified spin model for magnetic excitations in iron chalcogenides." <i>Physical Review B,</i> 96, no. 17 (2017) American Physical Society: https://doi.org/10.1103/PhysRevB.96.174403.https://hdl.handle.net/1911/99242Recent inelastic neutron scattering (INS) measurements on FeSe and Fe(Te1−xSex) have sparked intense debate over the nature of the ground state in these materials. Here we propose an effective bilinear-biquadratic spin model, which is shown to consistently describe the evolution of low-energy spin excitations in FeSe, both under applied pressure and upon Se/Te substitution. The phase diagram, studied using a combination of variational mean-field, flavor-wave calculations and density-matrix renormalization group (DMRG), exhibits a sequence of transitions between the columnar antiferromagnet common to the iron pnictides, the nonmagnetic ferroquadrupolar phase attributed to FeSe, and the double-stripe antiferromagnetic order known to exist in Fe1+yTe. The calculated spin structure factor in these phases mimics closely that observed with INS in the Fe(Te1−xSex) series. In addition to the experimentally established phases, the possibility of incommensurate magnetic order is also predicted.engArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.Journal articleUnified-spin-modelhttps://doi.org/10.1103/PhysRevB.96.174403