How to break armor as spellcaster?

As the title asks:
How do I break armor for my phys-spells to do more damage?

I use vulnerability, but this just lowers it to some amount.

Is there a support-gem I am missing, that could help with that? I don't want to go poison+corrosion, but have no idea, how.

Any help or suggestion appreciated!

If you’re not using your weapon swap, you could use Gas Grenade with armor break support gems. It breaks even boss armor in ~3 seconds.

thx for the idea - i have a lithning-staff for shock, but actually it is not a necessity (love the new "everybody can cast"-mentality of PoE2).

And a crossbow on the back looks cool, too :)

Edit: Splinter works with spells. Problem solved :D