Dissertation Committee Chair: Professor Steve Rolston and Professor Steven Anlage
Committee:
Professor Alicia Kollár
Professor Kasra Sardashti
Professor Christopher Jarzynski
Abstract: The iron-based superconductor FeTeSe has emerged as a promising platform for combining superconductivity and topology for the realization of topological quantum computing. Additionally, the unconventional S+/- pairing symmetry has been shown to give rise to higher-order topological surface states in FeTeSe. Despite the interest in superconducting devices based on FeTeSe, there have been relatively few demonstrations of Josephson junctions in FeTeSe-based systems.
In this dissertation presentation, we will begin by providing an overview of the iron-based superconductor FeTeSe. Next, we will describe the Josephson effects observed in a FeTe0.55Se0.45-based device. We will highlight three deviations from the typical Josephson effects: 1) the existence of two distinct Josephson diffraction patterns under applied RF irradiation; 2) sudden ‘jumps’ in the diffraction pattern as RF power increases; and 3) a minimum critical current at zero magnetic field when RF irradiation is present. Finally, we will discuss some potential phenomena that could be responsible for the unusual Josephson effects measured in this FeTe0.55Se0.45-based device.