Microwave Probing of Superconductivity in SrTiO3

SrTiO₃ is a wide-bandgap semiconductor with various unique physical properties. For example, it becomes superconducting upon electronic doping already at rather low charge densities. This superconducting state can be tuned with doping, leading to successively more electronic bands that contribute to the superfluid condensate. Corresponding to the critical temperature around 0.3K, the superconducting energy gap is around 20GHz and can thus be probed with microwave spectroscopy. In this project we want to address two aspects of superconducting SrTiO₃: Firstly, we want to understand the role of multi-band superconductivity by studying the microwave properties as a function of magnetic field. Secondly, we want to perform microwave spectroscopy on the superconducting interface between insulating SrTiO₃ and LaAlO₃. This superconducting interface can be controlled by applying a gate voltage, and thus offers fascinating prospects as a tuneable superconductor. These experiments would be the first to quantify the superconducting gap of the SrTiO3/LaAlO3 interface by microwave spectroscopy.