Effective perpendicular electric field as a probe for interlayer pairing in ambient-pressure superconducting La$_{2.85}$Pr$_{0.15}$Ni$_{2}$O$_{7}$ thin films

Recent angle-resolved photoemission spectroscopy (ARPES) experiments on La$_{2.85}$Pr$_{0.15}$Ni$_2$O$_7$ thin films have revealed a superconducting gap near the diagonal direction for the $d_{x^2-y^2}$ orbital, confined to a narrow momentum region. Our numerical calculations indicate that interlayer pairing is dominant, resulting in an $s_\pm$-wave symmetry. We propose employing perpendicular electric fields, a practical method in thin film systems, to verify the pairing symmetry. Our calculations predict that such fields will induce Fermi arcs or nodal points and significantly modulate the gap near the diagonal, with the modulated region overlapping the area probed by ARPES. This approach provides an effective tool for probing pairing symmetry in bilayer nickelate thin films, especially given current limitations in experimental techniques.