Past Events

Abstract
 

Scanning tunneling microscopy (STM) is a powerful tool for probing the materials microscopic electronic properties. In this talk I am going to present our recent low-temperature STM results on the iron-based superconductor LiFeAs and Mott Hubbard insulator Sr₂IrO₄. For the studies on LiFeAs, we took conductance spectroscopic mappings at temperatures between superconducting and normal phases. To our surprise, close to the Fermi energy long range density fluctuations around the intrinsic defects are observed. With careful analyses, we assign the observations to the inelastic coupling between tunneling electron and low energy bosonic modes of the material. Our results indicate that there is a previously little explored method, which can be used for probing the pairing glue in unconventional superconductors through individual defects. In addition, I will also list some of the open problems in this field which should be investigated in the near future. Insulator to metal transition is an important topic in strongly electronic correlated systems. We have also studied the electronic structure of Sr₂IrO₄, a Mott insulator with a large spin orbit coupling, with our low-temperature STM. I will present the results on how the defects affect the local electronic structure, and compare the defect behavior in Sr₂IrO₄ with the observations from other Mott insulators. Our results could be important for further tailoring its electronic properties in order to realize novel phases such as unconventional superconductivity.

Anyone interested is welcome to attend.