Stark many-body localization in spin chains with single-ion anisotropy

The interesting phenomena of many-body localization (MBL) has attracted a great deal of attention in condensed matter physics. Resulting from the intricate role of disorder in the dynamics of quantum states, one of the physical consequences is that if the system is initially in some non-equilibrium quantum state, it does not thermalize upon time evolution. This so-called localized regime is predicted to exist in a variety of systems. It has been shown that localization can be obtained even without disorder [1]. In this case, the localization is promoted by a nearly uniform gradient potential across an interacting quantum system and the phenomenon is termed Stark man-body localization (SMBL).

We have studied SMBL in a spin 1/2 Heisenberg chain with first and second nearest-neighbor couplings J₁ and J₂ [2]. We have shown that SMBL is very robust by inclusion of J₂. More interestingly, there are windows in the parameter space J₁-J₂ within which SMBL is actually enhanced. We also study SBML in a spin 3/2 Heisenberg model in the presence of single ion anisotropy. Our results for imbalance and entanglement entropy reveal a rich diagram over the J₁-J₂ parameter space, in which localization is obtained even in the absence of gradient potentials.

[1] M. Schulz, C. A. Hooley, R. Moessner, and F. Pollmann, Phys. Rev. Lett. 122, 040606 (2019).

[2] E. Vernek, Phys. Rev. B 105, 075124 (2022).