Speaker
Description
Incorporating magnetoelastic coupling into one-dimensional spin models makes them more realistic and can introduce novel physical phenomena. We investigate the deformable quantum spin-$1/2$ XX chain in a transverse magnetic field, which is exactly solvable within a combination of Jordan-Wigner and Fourier transformations. Lattice deformations are introduced into this quantum spin-chain model by accounting for a magnetoelastic coupling that depends linearly on a lattice distortion [1]. The primary outcome of our calculations is the variational Gibbs free energy, which is minimized with respect to a small distortion parameter. Subsequently, we compute the magnetization and magnetic susceptibility as fundamental indicators of the magnetic properties. In addition, we have also examined in detail the respective behavior of elastic properties such as the equilibrium value of the distortion parameter and inverse compressibility. The rigid spin-$1/2$ XX chain exhibits a quantum phase transition driven by the transverse magnetic field. In the deformable spin-$1/2$ XX chain in the transverse magnetic field we contrarily uncover first-order transition line extending from zero to finite temperatures, which eventually terminates at a critical point associated with a continuous thermal phase transition. The thermal first-order phase transitions emerging at sufficiently low temperatures are accompanied with a magnetic hysteresis, which is gradually suppressed by increasing temperature.
Acknowledgements
This work was financially supported by The Ministry of Education, Research, Development and Youth of the Slovak Republic under the grant No. VEGA 1/0298/25, by the Slovak Research and Development Agency under Contract No. APVV-22-0172, and by the internal grant of Faculty of Science of Pavol Jozef Šafárik University in Košice under the contract No. VVGS-2025-3497.
References
[1] O. Derzhko et al., “Compressibility of deformable spin chains near quantum critical points,” The European Physical Journal B, vol. 86, no. 3. Springer Science and Business Media LLC, Mar. 2013. https://doi.org/10.1140/epjb/e2013-30979-4
