Regensburg 2016 – scientific programme
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O: Fachverband Oberflächenphysik
O 81: Oxides and Insulator Surfaces I
O 81.1: Invited Talk
Thursday, March 10, 2016, 10:30–11:00, H4
Imaging orbitals and defects in superconducting FeSe/SrTiO3 — Jennifer Hoffman1,2, •Dennis Huang1, Tatiana Webb1, Shiang Feng1, Can-Li Song1,3, Cui-Zu Chang4, Jagadeesh Moodera4, and Efthimios Kaxiras1 — 1Harvard University, Cambridge, MA, USA — 2University of British Columbia, Vancouver, Canada — 3Tsinghua University, Beijing, China — 4Massachusetts Institute of Technology, Cambridge, MA, USA
Single-layer FeSe grown epitaxially on SrTiO3 has been shown to superconduct with Tc as high as 100 K, more than a factor of 10 higher than bulk FeSe. This dramatic enhancement motivates intense efforts to understand the superconducting mechanism and to design and fabricate devices. Nematic order, breaking the 4-fold rotational symmetry of the crystal, has been proposed as an important factor in the superconducting phase diagram. Meanwhile, atomic defects, which may pin nematic fluctuations or otherwise perturb superconductivity, can provide important clues into the superconducting mechanism as well as practical routes to superconducting devices. Here we use scanning tunneling microscopy (STM) to search for orbital nematicity in single-layer FeSe/SrTiO3, and to investigate atomic-scale defects which locally influence superconductivity. From quasiparticle interference (QPI) images, we disentangle scattering intensities from the orthogonal Fe 3dxz and 3dyz bands, and quantitatively exclude pinned nematic orbital order with domain size larger than δ r ∼ 20 nm. Furthermore, we identify a prevalent “dumbbell”-shaped atomic-scale defect whose placement could be harnessed to define two-dimensional superconducting devices.