Majorana edge modes in number-conserving models with long-range interactions

Abstract: Topological superconductors are believed to host exotic quasiparticle excitations known as Majorana zero-modes, with much of the evidence based on BCS mean-field theory. The direct application of mean-field arguments is tenuous in finite, isolated systems relevant in some experiments. Here, we numerically study fermion number-conserving models with long-range interactions, which under periodic boundary conditions exhibit robust topological and non-topological superconductivity, tuned by the strength of interaction [1]. We find evidence that, on the topological side, Majorana edge modes appear in open chains, manifesting as the vanishing of the energy splitting between odd- and even-parity ground states with increasing system size. Additionally, off-diagonal two-point correlation functions show nonlocal, parity-dependent edge effects consistent with Majorana phenomenology. We develop a correlation-based method revealing the spatial structure of Majorana modes in this fully interacting many-body setting.