When trying to decide if a certain piece of behavior should be a use case you should look to the "observable result" for the main actor. Does "login" yield such a result?

It depends on the system you are developing, the complexity of the authentication system etc. It might be a mere step in the use case scenario or it might become a (secondary) use case.

Another tool I teach my students is the BOSS test. You have to ask yourself:

Will my boss be happy when I 100 times today?

Usually usecases like "Login" fail the BOSS test. Things like "Create Order" or "Pay Invoice" usually pass the BOSS test.

But again whether or not to make a use case depends on your methodology (granularity of your use cases), on your system, and on the complexity. There is no YES/NO answer.