Simulating spin dynamics of supersolid states in a quantum Ising magnet

Motivated by a recent experimental study on the quantum Ising magnet K2Co(SeO3)2 that presented spectroscopic evidence of zero-field supersolidity (Chen et al., arXiv:2402.15869), we simulate the excitation spectrum of the corresponding microscopic XXZ model for the compound using the recently developed excitation ansatz for infinite projected entangled-pair states. We map out the ground state phase diagram and compute the dynamical spin structure factors across a range of magnetic field strengths, focusing especially on the two supersolid phases found near zero and saturation fields. Our simulated excitation spectra for the zero-field supersolid "Y"phase are in excellent agreement with the experimental data, recovering the low-energy branches and integer quantized excited energy levels ωn=nJzz. Furthermore, we demonstrate the nonlocal multi-spin-flip features for modes at ω2, indicative of their multimagnon nature. Additionally, we identify characteristics of the high-field supersolid "ψ"phase in the simulated spectra, which should be compared with future experimental results.