How do I reach just the moderators of physics stack exchange by email?
You probably shouldn't. If you have an issue on the site that needs moderator attention, flag it.
If, for some reason other than that, you want to contact the moderators, either leave a message in the chat room or use an @-notification on a question or answer that one of us has posted or commented on.
If you can't use the features the site provides to contact moderators (for example, if you aren't able to log in), email firstname.lastname@example.org, and the Stack Exchange team will help you out. That email address doesn't go to the site moderators, but in cases like that there's probably nothing we could do about it anyway.
(Personally, I do list an email address where I can be reached on my profile, but it shouldn't be used for matters relating to this site.)