This step is not atomic, you trust the mint to give you ecash. I don't think you can do it atomically.

Very cool! Congrats on the grant. Have you given any thought to TapAss stable coins? Do you think it would compete with this proposal, or be orthogonal, or complementary?

Pay ln invoice to receive ecash. Can that be made atomic with PTLCs? Instead of hash preimage buy a private key as the proof of payment. If the mint pre-commits to the (blind) signature nonce R (similar to DLCs) the lightning invoice could use s*G as the point to pay to. The payer would verify that this point is hash(R,msg)*P+R to know that the proof of payment will actually be the expected ecash (signature)