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Factorization, coherence and asymmetry in the Heisenberg spin-1/2 XXZ chain a transverse magnetic field and with Dzyaloshinskii-Moriya interaction

We investigate the factorization, coherence and asymmetry properties of the 1d Heisenberg spin-1/2 XXZ chain with Dzyaloshinskii-Moriya interaction (DMI) and a transverse magnetic field using quantum information measures. Both longitudinal and transverse DM vectors are considered. Using numerical DMRG, we compute the one-tangle, two-spin concurrence and the Wigner-Yananse-skew information. We show that a longitudinal DMI destroys the factorizability property while a transverse DMI preserves it. We relate the absence of factorizability to the breaking of the $U(1)$ rotation symmetry about the local magnetization axis at each lattice site. Physically, breaking of the symmetry manifests in the existence of a chiral current. Although the longitudinal DMI destroys factorizability, we obtain a `pseudofactorizing' field ($h_{pf}$) at which entanglement and hence violation of the $U(1)$ symmetry is minimal. Our calculations indicate a phase coherent ground state at $h_{pf}$. An entanglement transition (ET) occurs across this field which is characterized by an enhanced but finite range of two-spin concurrence in its vicinity in contrast with the diverging range of the concurrence for the ET across the factorizing field ($h_{f}$). We relate the asymmetry to the `frameness' or the ability for the state to act as a reference frame for some measurement. In absence of longitudinal DMI (or in presence of transverse DMI), at $h_{f}$, the single site magnetization axis specifies the common $z$-axis for the full system but not the full Cartesian reference frame due to a lack of phase reference. On the other hand, in the presence of a longitudinal DMI, our results indicate that at $h_{pf}$, the local magnetization and the chiral current are sufficient to specify the full Cartesian reference frame, with the chiral current being the macroscopic quantity to determine the phase reference.