Seminar By Vidya Mahdavan,University of Illinois
Title: Quasiparticle Interference and Strong Electron-Mode Coupling in the Quasi-One-Dimensional Bands of Sr2RuO4
Abstract:The single-layered ruthenate Sr2RuO4 has attracted a great deal of interest as a spin-triplet superconductor with an order parameter that may potentially break time reversal invariance and host half-quantized vortices with Majorana zero modes. While the actual nature of the superconducting state is still a matter of controversy, it has long been believed that it is condensed from a metallic state that is well described by a conventional Fermi liquid. In this talk I will show the first high resolution Fourier transform scanning tunneling spectroscopy (FT-STS) measurements on Sr2RuO4 obtained in the normal state. We use a combination of FT-STS and momentum resolved electron energy loss spectroscopy (M-EELS) to probe interaction effects in the normal state of Sr2RuO4. Our high-resolution data show signatures of the β-band with a distinctly quasi-one-dimensional (1D) character. The band dispersion reveals surprisingly strong interaction effects that dramatically renormalize the Fermi velocity, suggesting that the normal state of Sr2RuO4 is that of a `correlated metal’ where correlations are strengthened by the quasi 1D nature of the bands. In addition we observe kinks at energies of approximately 10meV, 38meV and 70meV are observed. I will discuss comparisons with M-EELS data, which show that the two higher energy features arise from coupling with collective modes. As time permits I will also show premiliminary STM data below Tc.The strong correlation effects and the kinks in the quasi 1D bands may have important implications for the superconducting state.