Local magnetic measurements of unconventional superconductors
Prof. Katja Nowack, Cornell University
A defining property of a superconductor is its response to an applied magnetic field. In this talk, I will discuss how we use scanning superconducting quantum interference devices (SQUIDs) to study the local magnetic response in two different types of superconductors. First, I will discuss measurements on focus ion beam (FIB) defined microstructures fabricated from single crystals of the heavy-fermion superconductor CeIrIn5. Using a scanning superconducting quantum interference device (SQUID) we observe that the superconducting transition temperature, Tc, varies throughout the structure in a complex pattern. This pattern arises due to the interplay of a non-trivial strain field from the differential thermal contraction of the substrate and microstructure and the sensitivity of Tc in CeIrIn5 to the strength and direction of strain. Devices with different geometry show that the spatial modulation of Tc can be tailored in agreement with predictions based on finite element simulations. These results offer a new approach to manipulate strain-sensitive electronic order on micrometer length scales in strongly correlated matter. Second, I will show how we use scanning SQUID to perform local magnetic measurements on few-layer van der Waals superconductors. We can directly probe the diamagnetic response as a function of temperature and other tuning parameters despite the extremely small sample volume. I will discuss how we can extract the superfluid stiffness and other characteristics of the superconducting state from our measurements.
All interested persons are invited to attend remotely—email physics@nd.edu for information.