Rajdip Banerjee | Searcharxiv

arXiv2026

Interplay of Anisotropy, Dzyaloshinskii Moriya Interaction and Symmetry breaking Fields in a 2D XY Ferromagnet

A two dimensional classical ferromagnetic XY model with its bound vortex-antivortex dominated quasi long range ordered phase at low temperatures is a long standing as well as well studied problem of interest in the field of condensed matter. We conduct a detailed Monte Carlo study of such model in a square lattice with rather unexplored extensions where additional anisotropic exchange coupling and Dzyaloshinskii-Moriya interactions (DMI) together affect the Kosterlitz-Thouless (KT) transition in presence/ absence of symmetry breaking fields. Without DMI, the exchange term promotes collinear (ferromagnetic) order, whereas the DMI term induces spin cantings. By tuning anisotropy upto Ising limit, we document energy, specific-heat, magnetizations as well as helicity modulus and vortex densities for different temperatures and DMI strength. We also compute the 2nd moment of correlation lengths in order to probe the spatial correlation of the spins. Furthermore, the effect of U(1) symmetry breaking 4-fold and 8-fold symmetric h4 and h8 fields are explored which shows how the double-peaked specific heat profiles changes in presence of DMI. Overall, our findings append many important updates in the low temperature phases of a topological XY ferromagnet when additional DMI and isotropy-breaking exchange and/or field terms are considered thereby providing a few practical blueprints for suitably engineering topological spin systems.

cond-mat.str-el↗

arXiv2025

Reviewing Current-Driven Dynamics and Monte Carlo based Analysis of Thermodynamic Properties of a Magnetic Skyrmion Crystal

Magnetic skyrmions with its topologically protected, nano-sized spin textures have already earned immense fame as information carriers due to their stability and low-current mobility. While ferromagnetic skyrmions suffer from a transverse deflection (i.e., the skyrmion Hall effect), their anti-ferromagnetic counterparts promise straight-line motion and ultrafast dynamics. Here we present a numerical study of the dynamics of lattice-based antiferromagnetic skyrmions driven by spin-transfer torque for which the Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation is solved using a fourth-order Range-Kutta integration. Then we conduct a detailed Monte Carlo study of the two-dimensional classical XY model to quantify how spatial anisotropy and Dzyaloshinskii-Moriya (DM) coupling reshape its thermal response across multiple lattice sizes. By tuning the ratio Jy/Jx, we document a systematic evolution of the specific-heat anomaly. For example, in the quasi-one-dimensional limit, CV exhibits a broad, low-temperature hump, whereas stronger anisotropy yields sharper peaks that migrate to higher inverse temperature. Finite-size scaling confirms the crossover from quasi-1D fluctuations to a two-dimensional Kosterlitz-Thouless transition. Incorporating a DM interaction further enriches this landscape. At D/J = 0.1, the main peak shifts modestly upward and is slightly suppressed; raising D/J elevates the peak magnitudes and creates a pronounced low-temperature plateau. This residual CV signals enduring chiral excitations and complex spin-twist textures beyond simple vortex unbinding. Our findings chart how directional and chiral couplings can be harnessed to tune pseudo-critical temperatures and thermodynamic signatures in two-dimensional magnets, providing a practical blueprint for engineering topological spin systems.

cond-mat.str-el↗