Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 15: Superconductivity: Fe-based Superconductors - Other Materials and Theory

TT 15.11: Vortrag

Montag, 1. April 2019, 18:00–18:15, H23

Symmetry-resolved strain tuning of composite nematic order — •Roland Willa, Max Fritz, and Jörg Schmalian — Institute for Theory of Condensed Matter, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany

Electronic nematicity in iron pnictide superconductors and charge order in the high-Tc cuprates are two phenomena that are associated with the appearance of composite order. The response of these systems to external strain has proven to be a powerful tool to study their symmetry properties [1,2]. We deploy a long-wavelength field theory to investigate the nematic transition temperature and excitation spectrum of a low-dimensional system under strain. In certain symmetry channels, strain lifts the degeneracy of the nematic order—similar to magnetic field lifting the degeneracy of Ising spins—and a crossover replaces the phase transition. In degeneracy-preserving strain channels, we find a quadratic dependence of the transition temperature with respect to strain. The magnitude of this effect as the system approaches the 2d limit reveals a logarithmic divergence for specific symmetry channels (Bng sector), while evaluating to order unity in others (Ang sector). This finding is in good agreement with the strong effects observed in the B1g-channel of Ba(Fe0.975Co0.025)2As2, as reported in Ref. [2], and underlines the importance of anisotropy in this system.
H.-H. Kim et al., Science (accepted)
M. Ikeda et al., arXiv:1803.09273 (2018)

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