Many-body localization properties of fully frustrated Heisenberg spin-1/2 ladder model with next-nearest-neighbor interaction

Geometric frustration and quasi-one-dimensionality present a rich arena for probing the stability and criticality of the many-body localization (MBL) transition. In this article, we investigate the many-body localization (MBL) properties of a fully frustrated Heisenberg spin-1/2 ladder model and compare them with a single-chain model using exact diagonalization. While both models exhibit standard MBL signatures, the frustrated ladder demonstrates enhanced stability against localization, requiring substantially stronger critical disorder. This conclusion is reinforced by a significant upward drift of the critical point with system size, where linear extrapolation to the thermodynamic limit suggests true critical points at approximately Wc(∞)∼ 15.33 for the ladder and 11.68 for the chain, indicating that our finite-size estimates (w2∼ 10.5 ±0.5 and w1∼ 7.5 ±0.5) should be interpreted as lower bounds. Our work demonstrates that geometric frustration not only enhances the stability of the MBL phase but may also influence the underlying critical scaling, offering new insights into the role of dimensionality and interactions in disordered quantum systems. Dynamical probes including entanglement entropy, fidelity, and magnetization clearly distinguish the thermal phase, showing rapid thermalization with volume-law entanglement, from the MBL phase characterized by slow logarithmic entanglement growth and memory preservation. The peak in entanglement entropy variance below the global transition marks the Griffiths regime, where rare thermal regions cause enhanced fluctuations. Finite-size scaling yields a critical exponent for the ladder model more consistent with the Harris bound than the chain model’s. Furthermore, the better data collapse for a continuous transition compared to a Kosterlitz–Thouless type is interpreted as reflecting the pre-asymptotic regime of our small systems rather than definitively identifying the universality class. This work extends MBL studies to frustrated quasi-1D geometries and highlights the critical importance of accounting for finite-size effects in disordered quantum systems.