When Conformal Interfaces Become Logarithmic

We construct conformal interfaces having defect conformal manifolds between two-dimensional rational CFTs, at least one of which is non-unitary. In a continuous family, interfaces with real and complex spectra can be marginally deformed to each other via their defect moduli parameters. An exceptional point then arises along the trajectory in the conformal manifold, where two interface operators with complex conjugate weights coalesce into a logarithmic pair. We reconstruct the entire trajectory of this novel spectral collision, independently, from self-annulus partition functions and bulk two point correlators in the presence of the interfaces.