We recently observed a new kind of collective excitation called a “demon”. This “particle” was predicted by David Pines in 1956, but it was never observed until we saw it in Sr2RuO4 in our momentum-resolved EELS experiments. Demons are interesting because they are massless and neutral, and do not couple to light, but can have […]
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Summer 2023
Two undergraduates have left our group, Nathan Manning, who accepted a position at Bruker, a manufacturer of scientific instruments, and Solomon Michalak, who is entering the Ph.D. program at the University of Minnesota, and Muhammad (Mo) Fadag, who was hired as a patent examiner at the USPTO. This summer, we have a team of new […]
Stranger than metals
The discovery of strange metals dates back three decades to when they were first encountered within a family of high-temperature superconductors known as cuprates. Superconductors, below a critical temperature, exhibit zero resistance to the flow of electrical current. In the superconducting state, electrons cease to behave as independent particles (scattering off one another and phonons) […]
A common mechanism for CDW order in all copper-oxide superconductors
Our latest collaboration with Eduardo Fradkin, Greg MacDougall, and Steve Kivelson, among many others, explains the widely varying CDW behavior across all families of copper-oxide superconductors. Using resonant soft x-ray scattering (RSXS) and neutron scattering, we studied a high-temperature superconductor, LESCO, that, at low temperatures, displays the characteristics of YBCO and Bi-based cuprates (blue line), […]
Three distinct charge density waves in a nematic superconductor
We have now observed three distinct charge density waves in the nematic superconductor, Ba1−xSrxNi2As2 (BSNA). This pnictide material has the same structure as the 122-phase FeAs superconductors, but contains Ni instead of Fe. Paglione’s group at the University of Maryland recently observed a sixfold enhancement of superconductivity in this material due to nematic fluctuations near […]