Overlaps of $q$-raised N\'eel states with XXZ Bethe states and their relation to the Lieb-Liniger Bose gas

Abstract

We present a Gaudin-like determinant expression for overlaps of $q$-raised N\'eel states with Bethe states of the spin-1/2 XXZ chain in the non-zero magnetization sector. The former is constructed by applying global $U_q(sl_2)$ spin raising operators to the N\'eel state, the ground state of the antiferromagnetic Ising chain. The formulas presented are derived from recently-obtained results for the overlap of the N\'eel state with XXZ Bethe states. The determinants as well as their prefactors can be evaluated in the scaling limit of the XXZ spin chain to the Lieb-Liniger Bose gas. Within this limit a $q$-raised N\'eel state that contains finitely many down spins corresponds to the ground state of free bosons. This allows for a rigorous proof of the BEC Lieb-Liniger overlap formula for an arbitrary number of particles.