Modularity of elliptic curves over cyclotomic ${\mathbb{Z}}_p$-extensions of real quadratic fields

We prove that all elliptic curves defined over the cyclotomic ${\mathbb{Z}}_p$-extension of a real quadratic field are modular under the assumption that the algebraic part of the central value of a twisted $L$-function is a $p$-adic unit. Our result is a generalization of a result of X. Zhang, which is a real quadratic analogue of a result of Thorne.