We use a solenoid to drive magnetic fields in our sample (RF frequencies, near field), but yes, we do often envision an absorption or emission event by a given nuclear spin as it changes its spin state in the presence of an even stronger, static magnetic field. We have to carefully match the frequency of the driving magnetic field to the so-called Larmor frequency of the spins, which allows them to absorb the supplied energy.

We're working on understanding possible applications now, and we also wonder whether this is a more commonly available phenomenon than originally thought. As experimentalists, we're very conservative in our claims -- for instance, we explain our observation of the "DTC signature" specifically proposed by theorists, without making claims as to the final interpretation of the results for the existing theory. Instead, our job is to very clearly explain what we did and what resulted, and then we get to see (and in some ways participate in) how the broader condensed matter community comes to understand the phenomena. It's an exciting position to be in, there are still many interesting unknowns!