We calculate the magnetic excitation spectrum in the stripe phase of high-$T_c$ materials. The stripes are modeled as coupled spin-$1∕2$ ladders and the spin dynamics is extracted using quantum Monte Carlo simulations, which can capture the strong quantum fluctuations near quantum critical points of coupled spin ladders. We find a characteristic hourglass magnetic excitation spectrum with high-energy peaks rotated by 45° compared to the incommensurate low-energy peaks in quantitative agreement with experimental data. The excitations are investigated as a function of interladder coupling, ladder width, and domain formation with stripe disorder.

• Received 9 August 2006

DOI:https://doi.org/10.1103/PhysRevB.75.012506