Ising-nematic spin correlations in the tetragonal state of uniaxial strained BaFe$_{2-x}$Ni$_x$As$_2$

ORAL

Abstract

Superconductivity in iron pnictides can be derived from electron or hole-doping to their antiferromagnetic (AF) ordered parent compounds. In the normal state above the superconducting transition temperature (Tc), an in-plane resistivity anisotropy has been observed in uniaxial strained iron pnictides BaFe$_{2-x}$T$_x$As$_2$ (T $=$ Co, Ni) near the AF ordered state. This anisotropy has been suggested as a signature of the spin Ising-nematic phase that breaks the in-plane four-fold rotational symmetry of the underlying tetragonal lattice, but direct evidence for a spin nematic state is lacking. Here we use inelastic neutron scattering (INS) to show that low-energy spin excitations in uniaxial strained BaFe$_{2-x}$Ni$_x$As$_2$ (x $=$ 0, 0085) change from four-fold symmetry to two-fold symmetry in the tetragonal phase at temperatures corresponding to the onset of the in-plane resistivity anisotropy. Our results thus indicate that spin excitation anisotropy plays a crucial role in the electronic nematic behavior of iron pnictides.

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Authors

  • Xingye Lu

    Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences

  • Jitae Park

    Heinz Maier-Leibnitz Zentrum (MLZ), TU Munchen

  • Rui Zhang

    Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences

  • Huiqian Luo

    Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences

  • Andriy Nevidomskyy

    Rice University, Department of Physics and Astronomy, 6100 Main St., Houston, TX 77005, Department of Physics, Rice University, Rice University, Department of Physics and Astronomy, Rice University

  • Qimiao Si

    Rice University, Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA, Physics \& Astronomy Department, Rice University, Department of Physics and Astronomy, Rice University, Department of Physics and Astronomy, Rice University, Houston 77005

  • Pengcheng Dai

    Rice University, Physics Dept, Department of Physics and Astronomy, Rice University, Rice Univ, Rice University