Electronic nematic susceptibility of iron-based superconductors
| Date/Time: | Thursday, 13 Nov 2014 - Thursday, 13 Nov 2014 |
|---|---|
| Location: | PHYSICS Hall Room 3 |
| Phone: | 515-294-5630 |
| Channel: | College of Liberal Arts and Sciences |
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Superconductivity in the iron-based materials occurs when a spin-density-wave (SDW) transition of the parent compound is suppressed by either physical pressure or through chemical doping. Associated with the SDW transition is a structural transition, which breaks the four-fold rotational symmetry of the high-temperature phase. The structural transition is thought to be driven by electronic degrees of freedom (spin and/or orbital), fluctuations of which may drive the superconducting pairing. Here, we study the 'nematic' susceptibility [1], i.e., the susceptibility associated with the electronic ordering that leads to the structural transition. The results are based mainly on shear-modulus measurements using a three-point-bending method in a capacitance dilatometer [2] and are complemented by thermal-expansion and NMR measurements. Results on hole-doped and electron-doped BaFe2As2, as well as on FeSe, are discussed and compared in the framework of the spin-nematic theory [3]. FeSe is particularly interesting in this context, because it might be thought of as a purely nematic phase, i.e., a structurally distorted phase without magnetic order. The comparison of these different systems allows an attempt to differentiate the role of spin and orbital degrees of freedom in the physics of the iron-based materials [4].
[1] R. Fernandes et al., PRL 105, 157003 (2012) [2] A. Böhmer et al., PRL 112, 047001 (2014) [3] R. Fernandes et al., PRL 111 037001 (2013) [4] A. Böhmer et al., arxiv 1407.5794 (2014)