Quantum properties of a strongly interacting frustrated disordered magnet

We compute the low-energy quantum states and low-frequency dynamical susceptibility of a quantum generalization of the two-dimensional Edwards-Anderson spin glass, obtaining exact numerical results for system sizes much larger than previously accessible. The ground state is a complex superposition of a substantial fraction of all the classical ground states, often having large connected regions of spins all exhibiting strong quantum fluctuations, and yet the dynamical susceptibility exhibits sharp resonances reminiscent of the behavior of single spins. The dependence of the energy spectra on system size differs qualitatively from that of the energy spectra of random undirected bipartite graphs with similar statistics, implying that strong interactions are giving rise to these unusual spectral properties.