The Cusp at Optimum Doping in the Low-Temperature Hall Number of the High-Temperature Superconductors – Greg Boebinger

Date: Wed. October 25th, 2006, 4:15 pm-5:15 pm
Location: Rockefeller 301

After a brief overview of recent achievements at the National High Magnetic Field Laboratory (MagLab) using our pulsed, powered, and persistent magnets, I will focus on a series of my own experiments that utilized 60T pulsed magnetic fields to suppress the superconducting state in the high-temperature superconductors. The pulsed magnets are operated to the point of catastrophic stress failure…and occasionally, inadvertently, beyond. Oddly, however, they seem to offer the gentlest way to reveal the low-temperature normal-state of the cuprates in the absence of superconductivity. Evidence from resistivity measurements suggests a metal-insulator transition underlying the superconducting state. More recently [Nature 424, 912 (2003) and unpublished], we report Hall effect measurements that show a cusp in the low-temperature Hall number at optimum doping, as if the system has an enhanced number of carriers in proximity to a phase transition at optimum doping.