Decoherence of spinons in perturbed spin-chain systems

Fractionalized excitations in quantum magnets such as 1D Heisenberg S=1/2 systems (spinons in S=1/2 XXX chains) present evidence of quantum entangled states. Such topological excitations are known to have long lifetimes due to the properties of integrable systems, which host an infinite number of conserved quantities. Thus, scattering processes between quasiparticles conserve information, whereas in most systems such processes lead to damping or decoherence. In fact, our recent neutron scattering work studying such spin-chains demonstrates an absence of collisional damping even when thermal fluctuations are much stronger than the energy-scale of interactions between spins.



We now present further investigations of S_eff=1/2 spin-chains using magnetic field, temperature, and laser excitation to perturb chains in their low-temperature limit and observe the resulting decoherence phenomena. From inelastic neutron scattering and resonant inelastic x-ray spectra (RIXS) we compute direct-time-direct-space correlation functions and examine the evolution of the spin density as a function of these various perturbations of the S_eff=1/2 quantum spin-chain Hamiltonian. We further compute the quantum Fisher information to place lower bounds on multipartite entanglement as the chains are driven through various field and temperature-dependent phase transitions, and as laser-light excites electronic transitions of magnetic ions.