Colloquium

Gaps in our understanding:  STM studies of the pseudogap phase of high temperature superconductors

Dr. Eric Hudson
MIT
Wednesday, February 27, 2008
Higgins 310, 4 pm

The nature and behavior of electronic states in high temperature superconductors are the center of much debate. The pseudogap state, observed above the superconducting transition temperature TC, is seen by some as a precursor to the superconducting state. Others view it as a competing phase. Recently, this discussion has focused on the number of energy gaps in the system. While some experiments indicate a single energy gap, implying that the pseudogap is a precursor state, others indicate two, suggesting that it is a competing or coexisting phase. In this talk I will report on temperature and doping dependent scanning tunneling spectroscopy of (Bi-Pb)2Sr2CuO6+x. We have found a new, narrow, homogeneous gap that vanishes near TC, superimposed on the typically observed, inhomogeneous, broad gap, which is only weakly temperature dependent. These results, especially in combination with recent ARPES measurements, point strongly towards a two gap picture of the high temperature superconductors, in which distinct superconducting and pseudogaps coexist below TC.