PhD students publish without supervisors – how does it work?
I published two single-author journal articles during my PhD in a field where a PhD student publishing without their supervisor is uncommon. So uncommon, in fact, that I can't think of any other examples in my subfield.
My case is probably unusual in that by a few years into my project, I was far more of an expert in the subject than my supervisor. My former supervisor is a bit of a generalist, so this is not unusual for them. At a certain point during my PhD I started disagreeing strongly with my supervisor about what to do, which is when I started working more independently.
I actually would have been offended if I were required to put my supervisor's name on either paper, as they had negligible intellectual contributions to the papers and were even harmful to them in my opinion. My supervisor made it quite clear that the work was my own, and even stated so during my defense. (They already had tenure so I don't think they needed their name on the papers, though this could be a factor in other cases.)
From my own experience I can say there are advantages and disadvantages to publishing without one's supervisor as a PhD student.
Some researchers will have greater respect for a student who has published independently. I've been pleasantly surprised to be treated as an authority on certain subjects during my PhD. I admit that those people might just be nice all around, but I didn't see most students getting that sort of treatment.
Unfortunately there are people who are suspicious of more independent students. One reviewer brought up the fact that I was a PhD student publishing without my supervisor in their review, as if such a thing were something to be suspicious of. They did not elaborate about what they found suspicious, but in my response I wrote that they are welcome to ask the editor to contact my supervisor if they believe I had not credited others sufficiently. I've also been warned to emphasize successful collaborative work on my CV and cover letters when applying to jobs, as some people will assume that I'm hard to get along with if I work independently too much.
I personally prefer to work more independently. I think the current research environment incentivizes collaboration far too much. I see a lot of groupthink/lowest commmon denominator type thinking in much of heavily collaborative work. Good ideas are avoided too often simply because they are unfamiliar to most people whose approval is needed. Good research often comes from unfamiliarity.
That's not to say that collaboration is often bad, just that it's too often bad. I fully agree that certain projects are impossible without collaboration. But given the choice, I'd bias my own work towards what an individual can handle, which I think is more than most believe.