People have been putting moderate energy deuterons into deuterated materials since the 1930s. They typically do it by shooting ions at a target, but it's standard technology for making neutrons in small neutron generators, for example those used in oil well logging.

And it's well known this doesn't promise to produce fusion anywhere even close to breakeven.

If I had to bet, I'd say these researchers missed some confounding effect and are measuring an experimental artifact.