Title: Unconventional supersymmetric quantum mechanics in spin systems

Abstract: It is shown that the eigenproblem of a two-level Hamiltonian with non-zero off-diagonal terms is involved with a supersymmetry quantum mechanics. This is associated with an intertwining relation between the components of an eigenspinor which is exploited to reduce the spin degrees of freedom in a generic spin model. The scheme is illustrated with examples of spin-boson models including the Jaynes-Cummings model and generalized Rabi models. The generalization of the scheme to a single spin-$\frac{p}{2}$ is discussed. We also demonstrate how the supersymmetry can reduce the degrees of freedom of a many-spin system. Examples of the Tavis-Cummings model and generalized Dicke models are discussed by utilizing this formalism.