### HMC Physics Colloquium

Tuesdays at 16:30 in Shanahan Center for Teaching and Learning, Room B460

## Jenny Hoffman

Harvard University

Exploring a New Family of High-:mil:T_c Superconductors: the Iron-Arsenides

Jan. 27, 2009

I will give a review of superconductivity research over the last century, culminating in the recent, exciting discovery of a second family of high-$$T_c$$ superconductors based on iron and arsenic. We are now studying these new superconductors using a low temperature scanning tunneling microscope (STM), built with the help of two Harvey Mudd alums, now graduate students at Harvard. We have used this STM to image the superconducting density of electronic states with atomic resolution. We have also imaged a disordered lattice of magnetic vortices, which demonstrates strong bulk pinning in these new materials, a necessary condition for practical superconducting applications.