Kirk Duran Rose Hills
Identification of solid phases transition in BaFe2As2 using Resonant Ultrasound Spectroscopy
Superconductors are materials that exhibit the phenomenon of zero electrical resistance below a certain temperature. Some pure metals are superconductors, but only at very low temperatures. But over the last few decades some interesting materials have been discovered that super-conduct at high temperatures, up to about 200C. This is still far below room temperature, but if we can understand these materials it may be possible to engineer even room-temperature superconductors. However, many aspects of hightemperature superconductors are still unknown, including how the other properties of these materials are related to their superconductivity. For example, the ironbased superconductor BaFe2As2 undergoes a phase transition that changes its crystal structure. But there is debate whether this transition is related to superconductivity. Knowing exactly at what temperature the structural transition of BaFe2As2 occurs as a function of doping (chemical substitution) is an important part of answering this question.
Resonant Ultrasound Spectroscopy (RUS) is a technique for measuring the resonant frequencies of a material. By measuring how the frequencies change with temperature we can pinpoint where transitions occur between different states, as a phase transition will be accompanied by a sudden change in resonant frequencies. I propose to use RUS to determine at what temperature the structural phase transition occurs in a specific doping of BaFe2As2.