Simulating Spin Dynamics of Supersolid States in a Quantum Ising Magnet K₂Co(SeO₃)₂

Motivated by the recent neutron scattering experiments on a quantum Ising magnet K₂Co(SeO₃)₂ where spectroscopic evidence of zero-field supersolidity was presented [1,2], we simulate the excitation spectrum of the corresponding microscopic XXZ model for the compound, using the recently developed excitation ansatz of infinite projected entangled-pair states (iPEPS). [3] 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 ω_n=nJ_zz. Furthermore, we demonstrate the nonlocal multi-spin-flip features for those high-lying modes, indicative of their multi-magnon nature. Additionally, we identify characteristics of the high-field supersolid "Ψ" phase in the simulated spectra, to be compared with future experimental results.