Element Zero has always been a weird aspect of the Mass Effect universe: everyone uses it, but the codex doesn't explain its composition or effects beyond the regular mass effect fields. Does anyone here have any theories as to what the chemical (or non-chemical) composition of element zero is?

My original thought from searching the web was that it was a non-chemical element (i.e., neutronium, a material composed of only neutrons, not protons or electrons), but I'm not so sure of that now, especially after seeing some talk about the "zero" in element zero standing for its atomic mass (which changes if an electric current is run through it). I suppose the term "exotic matter" could work here, but I'd like to know everyone else's thoughts as well because I'm no physicist and video game lore interests me too much for me to not ask this question.

Hope you all have a good day.