Many-body characterization of topological superconductivity: The   Richardson-Gaudin-Kitaev chain
  What distinguishes trivial from topological superluids in interacting many-body systems where the number of particles is conserved? Building on a class of integrable pairing Hamiltonians, we present a number-conserving, interacting variation of the Kitaev model, the Richardson-Gaudin-Kitaev chain, that remains exactly solvable for periodic and antiperiodic boundary conditions. Our model allows us to identify fermionic parity switches that distinctively characterize topological superconductivity in interacting many-body systems. Although the Majorana zero-modes in this model have only a power-law confinement, we may still define many-body Majorana operators by tuning the flux to a fermion parity switch. We derive a closed-form expression for an interacting topological invariant and show that the transition away from the topological phase is of third order. 
Gerardo Ortiz, Jorge Dukelsky, Emilio Cobanera, Carlos Esebbag, and   Carlo Beenakker
cond-mat.mes-hall cond-mat.str-el cond-mat.supr-con math-ph math.MP nucl-th