Spring 2021 Physics Colloquium: The spin ladder to nowhere

Abstract: High temperature correlated electron superconductivity is one of the most exciting areas of condensed-matter physics, but more than 30 years after its discovery it is yet to be understood.  Many relatively simple (although still very difficult to solve) models have been proposed for the high T$_c$ cuprates since then. One common assumption has been that the oxygen atoms in the copper-oxygen planes may be ignored and a simpler Cu-only single-band model can explain
superconductivity. This model is well understood in the limit of a ladder, where spin singlets on each rung of the ladder take the place of Cooper pairs, and calculations on ladders find long-ranged superconducting correlations. In this talk we present results of large scale numerical calculations of pairing correlations on cuprate ladders, including both copper and oxygen orbitals. We find that in realistic cuprate ladder models the long-range superconducting order is suppressed.  This shows that ladder physics, now more than 25 years old, is not relevant to superconductivity in the cuprates. Our results strongly suggest that any minimal model must include the oxygen orbitals of the copper-oxygen planes. 

Please join us!