All-Optical and Microwave-Free Detection of Meissner Screening using Nitrogen-Vacancy Centers in Diamond.

Microscopic studies on thin film superconductors play an important role for probing non-equilibrium phase transitions and revealing dynamics at the nanoscale. However, magnetic sensors with nanometer scale spatial and picosecond temporal resolution are essential for exploring these. Here, we present an all-optical, microwave-free method, that utilizes the negatively charged nitrogen-vacancy (NV) center in diamond as a non-invasive quantum sensor and enables the spatial detection of the Meissner state in a superconducting thin film. We place an NV implanted diamond membrane on a superconducting LSCO thin film. The strong B-field dependence of the NV photoluminescence (PL) allows us to investigate the Meissner screening in LSCO under an externally applied magnetic field in a non-resonant manner.