学术报告 Imaging the exotic electrons in 4d- and 5d- transition metal oxide
【报告题目】 Imaging the exotic electrons in 4d- and 5d- transition metal oxide
【报 告 人】 Dr. WANG, Zhenyu (王震宇）
【时 间】 2017-12-08 星期五 3:00PM
【地 点】 理工楼801
In this talk, I will present some new results on layered ruthenate and iridates by using scanning tunneling microscopy/spectroscopy (STM/S). First, we use Fourier transform STS to probe the electron interactions in the normal state of Sr2RuO4, which becomes a spin-triplet superconductor below 1.5K. Our 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. We also observe kinks at energies of approximately 10meV, 38meV and 70meV in the dispersion that arise from coupling with collective modes. This experiment opens a unique approach to revealing the sub-meV superconducting gap structures in this compound. In the second part, I will show how the Mott insulating state in Sr3Ir2O7 collapses with electron doping (La) and isovalent substitutions (Ru) in strong spin-orbit coupling limit. Nanoscale phase separation, charge order and pesudogap are revealed in the electron doping case, showing generic features of doped Mott insulators. However, we find a novel mechanism of Mott transition in Sr3(IrRu)2O7 samples. Ru substitution does not introduce carriers in this system. Instead, it creates disorder without invoking additional order parameters and drives the insulator into an antiferromagnetic, metallic state. Our data suggest that V-shaped pesudogap may be an inevitable consequence of disorder in doped Mott insulators.
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