Generalized Bloch oscillations of doublon defect in one-dimensional antiferromagnetic atomic spin chain under linear and quadratic magnetic gradients
Phys. Rev. A 114, 033319 – Published 14 September, 2026
DOI: https://doi.org/10.1103/64hw-2yy1
Abstract
We investigate generalized Bloch oscillations of a single doublon defect in a one-dimensional antiferromagnetic chain subjected to linear and quadratic magnetic-field gradients. By mapping the spin-charge coupled many-body dynamics onto an effective single-particle model, we reveal how the Néel background mediates parity-dependent coupling between the defect and the external fields. The linear gradient induces a staggered potential that splits the Wannier-Stark ladder into two intertwined subladders, producing a characteristic beating pattern in the center-of-mass motion with a subband offset accurately captured by third-order perturbation theory. The quadratic gradient generates sublattice-dependent tilts that shear the ladder into a scissor-like profile, yielding site-dependent beating periods that encode the nonlocal spatial averaging of the defect wave function. When both gradients coexist, their interplay is fundamentally nonadditive: the quadratic gradient breaks the two-site periodicity that forbids second-order linear responses, unlocking a dominant cross-coupling proportional to . This leaves distinct fingerprints on the Bloch-oscillation spectrum—a rigid baseline shift of the fundamental doublet and asymmetric broadening of the first harmonic. These predictions are quantitatively corroborated by exact many-body simulations of the real-time density evolution and center-of-mass dynamics. Our work establishes a gradient-induced unlocking mechanism for multigradient defect spectroscopy in quantum magnets, offering a framework for probing parity-protected selection rules and their controlled breaking via generalized Bloch oscillations in tunable quantum simulators.
