Selected developments in ultra-low field magnetic resonance for fundamental physics and applications

Precise measurement of spin precession in small magnetic fields is a pathway to investigate a variety of new physics ideas like fundamental electric dipole moments and Axion-like particles. I will discuss a series of efforts using nuclear and electronic systems to perform such experiments, spanning from 3-He to neutrons, ions and atoms. With the development of a new extremely shielded environment at TUM with a background field at the 10-11 T level, we recently approached a previously hard-to-reach regime, where the interaction of the spins is large compared to the NMR field. The developments allow for thoroughly investigating systematic issues for EDM experiments. This is in
particular interesting for a next generation search of the EDM of 129Xe, but it also enables interesting applications like biosignal measurements as from fetal hearts or the human brain. Next to an overview of first experimental results and its power to e.g. reconstruct the ion-current flow in the heart muscle, some insights into the work at these conditions will be given.