|"Novel Magnetism in New Heavy Electron Compounds" |
Physics and Astronomy
Stony Brook University and Brookhaven National Laboratory
Room 385E 1:30 p.m. Serin Physics Lab.
Unconventional superconductivity has been observed in heavy electron compounds and in complex oxides near their `quantum critical points, where magnetic order only occurs at the lowest temperatures. The small energy scales characteristic of the heavy electron compounds and their separability allows us to conveniently study the full range of pertinent behaviors, from the physics of individual moments to their collective phenomena as the quantum critical point is approached. In order to understand the full range of conditions which favor heavy electron superconductivity, we are searching for new systems which can be tuned continuously and without compositional variation to the quantum critical point. One newly discovered system is Yb3Pt4, which makes a first order transition from a paramagnetic state with localized Yb moments into an antiferromagnetically ordered state where the moment is fully itinerant, best described as a strongly interacting Fermi Liquid. Magnetic fields can be used to tune the magnetic ordering transition to a critical endpoint, accompanied by the suppression of the ordered moment and the divergence of the quasiparticle mass in the Fermi Liquid. Unlike the general case in heavy electron systems, the ordered state in Yb3Pt4 seems to have a large Fermi surface, while the moments are localized and not participating in the Fermi surface in the paramagnetic state.