Wednesday Colloquium: Dr. Pengcheng Dai, Rice University  Add To Calendar

  • Date(s): Wednesday, 9/9 3:00 PM to Wednesday, 9/9 4:00 PM
  • Speaker: Dr. Pengcheng Dai
  • Host: Dirk Morr
  • Campus Address: 138 SES Science and Engineering South

Title: Ising-nematic spin correlations in the tetragonal state of uniaxial strained iron pnictides
 
Abstract: A determination of the microscopic origins of electronic phases in high-transition temperature (high-Tc) superconductors is important for understanding the mechanism of superconductivity. In the paramagnetic tetragonal phase, an in-plane resistivity anisotropy has been observed in the BaFe2−xTxAs2 (T = Co, Ni) iron pnictides, but its microscopic origin is unknown. Here we use inelastic neutron scattering to show that low-energy spin excitations in these materials change from four-fold symmetry to two-fold symmetry at temperatures corresponding to the onset of the in-plane resistivity anisotropy. Since both the resistitivy and spin excitation anisotropy vanishes near optimal superconductivity, we conclude that the spin Ising-nematic phase leads to the resistivity anisotropy and is also important for high-Tc superconductivity.

Colloq flyer 9-9 Dai