Exotic quantum holonomy and non-Hermitian degeneracies in the two-body Lieb-Liniger model

An interplay of an exotic quantum holonomy and exceptional points is examined in one-dimensional Bose systems. The eigenenergy anholonomy, in which a Hermitian adiabatic cycle induces nontrivial change in eigenenergies, can be interpreted as a manifestation of the eigenenergy's Riemann surface structure, where the branch points are identified as exceptional points, which are degeneracy points in the complexified parameter space. It is also shown that the exceptional points are the divergent points of the non-Abelian gauge connection for the gauge theoretical formulation of the eigenspace anholonomy. This helps us to evaluate anti-path-ordered exponentials of the gauge connection to obtain gauge covariant quantities.