Unique Signatures of Topological Phases in Two-Dimensional THz Spectroscopy.

We develop a microscopic theory for the two-dimensional (2D) spectroscopy of one-dimensional topological superconductors. We consider a ring geometry of an archetypal topological superconductor with periodic boundary conditions, bypassing energy-specific differences caused by topologically protected or trivial boundary modes that are hard to distinguish. We show numerically and analytically that the cross-peak structure of the 2D spectra carries unique signatures of the topological phases of the chain. Our work reveals how 2D spectroscopy can identify topological phases in bulk properties.