Magnetoelastic control of quantum correlations and field sensitivity in a spin-1/2 Heisenberg dimer

Abstract

We investigate the thermodynamic and quantum properties of a magnetoelastic spin-1/2 Heisenberg dimer, where the exchange interaction depends on the dimer displacement. By combining an exact treatment of the spin sector with a harmonic description of the vibrational degree of freedom, we obtain an effective model in which each spin configuration is associated with a distinct vibrational mode, leading to a non-factorizable partition function. We analyze the thermal behavior and identify regimes corresponding to entangled and fully polarized states. Quantum correlations are analyzed through concurrence and local quantum uncertainty, showing that while entanglement is rapidly suppressed by temperature, nonclassical correlations persist over a broader range due to the competition between spin sectors. We further examine the magnetic Fisher information, which provides a measure of the sensitivity of the system to the external magnetic field. Its behavior reveals enhanced response in crossover regions where magnetoelastic effects induce strong redistribution of the level populations. Our results demonstrate that magnetoelastic coupling plays a central role in controlling both quantum correlations and magnetic response, establishing a direct link between entanglement, nonclassical correlations, and thermodynamic sensitivity in coupled spin-dimer systems.