Time and place: 2019.3.29, 9:30 am, Wuhan National High Magnetic Field Center B206

Presenter: Haihu Wen

Title: Topological Superconductivity in Sr_xBi₂Se₃ and Bi₂Te₃/FeTe_0.55Se_0.45 heterostructures

Abstract：

Topological superconductor is a timely and frontier topic in condensed matter physics. Here we report superconductivity with twofold symmetry in some related materials. In Sr doped Bi₂Se₃, we find the nematic superconductivity from the c-axis transport measurements. Furthermore, we show the systematic study of scanning tunneling microscope/spectroscopy on Sr_xBi₂Se₃. We find that the surface Dirac electrons will simultaneously condense into the superconducting state within the bulk superconducting gap. We deposit Bi₂Se₃ thin film on the FeTe_0.55Se_0.45 substrate and get the proximity induced superconductivity. Within the vortex cores of FeTe_0.55Se_0.45, we observed the long sought discrete Caroli-de Gennes-Matricon bound states. By using the quasiparticle interference technique, we demonstrate clear evidence of twofold symmetry of the superconducting gap. The gap minimum is along one of the main crystalline axis following the so-called Δ4y notation. This is also accompanied by the elongated vortex shape. Our results reveal the direct evidence of superconductivity with two-fold symmetry in Bi₂Se₃ thin film.