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 ₍=nJₙₙ. Furthermore, we demonstrate the nonlocal multi-spin-flip features for modes at ₂, indicative of their multimagnon nature. Additionally, we identify characteristics of the high-field supersolid ``'' phase in the simulated spectra, which should be compared with future experimental results.