Tuning spin-density separation via finite-range interactions: Dimensionality-driven signatures in dynamic structure factors

Abstract: Spin-density separation, marked by distinct propagation velocities of spin and density excitations, epitomizes strong correlations, historically confined to one-dimensional (1D) systems. Recent ultracold quantum gas experiments, however, demonstrate its emergence in higher dimensions through precise tuning of intra- to interspecies interaction ratios, inspiring exploration of how dimensionality and interatomic interactions govern quantum correlations. We investigate this in two-component bosonic mixtures with finite-range interactions, probing 1D and three-dimensional (3D) dynamics. Using effective field theory within the one-loop approximation, we derive analytical expressions for zero-temperature ground-state energy and quantum depletion, seamlessly recovering contact interaction results in the contact limit. By crafting an effective action for decoupled density and spin modes, we compute dynamic structure factors (DSFs), revealing how finite-range interactions sculpt spin-density separation. A pivotal finding is the dimensionality-driven divergence in DSF peak dynamics: in 1D, peaks ascend to higher frequencies with increasing interaction strength, yielding sharp responses; in 3D, peaks descend to lower frequencies, with broader density wave profiles. These insights highlight dimensionality's critical role in collective excitations and provide a robust theoretical blueprint for probing interaction-driven quantum phenomena via Bragg spectroscopy, paving new pathways for exploring dimensionally tuned quantum correlations in ultracold quantum gases.