| Description |
Superconductivity is a unique state of matter observed at cryogenic temperatures in many materials. Superconductors are defined as materials that have zero DC electrical resistance and perfect diamagnetism below a critical transition temperature, Tc. These properties are very useful for many applications in research and industry. Superconductors are separated into two main classes: the conventional superconductors that are well described by BCS theory, which was the first predictive theory of superconductivity developed by Bardeen, Schrieffer, and Cooper in 1957, and the wide range of unconventional superconductors for which no overall theory to describe their superconducting properties or mechanisms has been developed. Unfortunately, no known superconductors-conventional or unconventional-have Tc‘s near room temperature, and the hunt for an ambient condition superconductor continues. The reason for this is because there remains a large gap in our understanding of the mechanisms behind superconductivity in unconventional superconductors, and also in our quantitative ability to theoretically predict the superconducting properties of even conventional superconductors. Overall, many questions remain, and numerous pathways towards understanding superconductivity are currently being explored. Pressure can give direct control over the density of a material and is thus a fundamental way to study superconductors due to the lattice's role in superconductivity. The goal of this project was to build and calibrate an AC susceptometer to measure the Tc of material while under high pressures inside a diamond anvil cell (DAC). Such a deviceis crucial to studying superconductors at high pressures and can help in our lab's efforts to answer compelling questions about superconductors, discover new superconducting materials under extreme conditions, and develop understanding of the mechanisms of superconductivity in unconventional systems. The constructed device is a mini-coil system (~2 mm diameter) employing solenoids of very fine copper wire (~40 micron diameter). The sample, under high-pressure conditions between the diamond anvils of the DAC, is situated inside the mini-coil where the onset of superconductivity can be registered by a change in the voltage across the coil. To test the effectiveness of the device, the Tc of lead as a function of pressure was measured. The measured value of the slope was -0.35 ± 0.03 GPa/K and was within error of the value measured by Clark et al. (1978) of -0.364 ± 0.001 GPa/K Given these results, this device can now be employed for future measurements of the Tc of superconductors under high pressure inside a DAC. |
