TY - JOUR T1 - Anomalous broadening in driven dissipative Rydberg systems JF - Physical Review Letters Y1 - 2016 A1 - E. A. Goldschmidt A1 - T. Boulier A1 - R. C. Brown A1 - S. B. Koller A1 - J. T. Young A1 - Alexey V. Gorshkov A1 - S. L. Rolston A1 - J. V. Porto AB - We observe interaction-induced broadening of the two-photon 5s-18s transition in 87Rb atoms trapped in a 3D optical lattice. The measured linewidth increases by nearly two orders of magnitude with increasing atomic density and excitation strength, with corresponding suppression of resonant scattering and enhancement of off-resonant scattering. We attribute the increased linewidth to resonant dipole-dipole interactions of 18s atoms with spontaneously created populations of nearby np states. Over a range of initial atomic densities and excitation strengths, the transition width is described by a single function of the steady-state density of Rydberg atoms, and the observed resonant excitation rate corresponds to that of a two-level system with the measured, rather than natural, linewidth. The broadening mechanism observed here is likely to have negative implications for many proposals with coherently interacting Rydberg atoms. VL - 116 U4 - 113001 UR - http://arxiv.org/abs/1510.08710 CP - 11 U5 - 10.1103/PhysRevLett.116.113001 ER - TY - JOUR T1 - 2D Superexchange mediated magnetization dynamics in an optical lattice JF - Science Y1 - 2015 A1 - R. C. Brown A1 - R. Wyllie A1 - S. B. Koller A1 - E. A. Goldschmidt A1 - Michael Foss-Feig A1 - J. V. Porto AB - The competition of magnetic exchange interactions and tunneling underlies many complex quantum phenomena observed in real materials. We study non-equilibrium magnetization dynamics in an extended 2D system by loading effective spin-1/2 bosons into a spin-dependent optical lattice, and we use the lattice to separately control the resonance conditions for tunneling and superexchange. After preparing a non-equilibrium anti-ferromagnetically ordered state, we observe relaxation dynamics governed by two well-separated rates, which scale with the underlying Hamiltonian parameters associated with superexchange and tunneling. Remarkably, with tunneling off-resonantly suppressed, we are able to observe superexchange dominated dynamics over two orders of magnitude in magnetic coupling strength, despite the presence of vacancies. In this regime, the measured timescales are in agreement with simple theoretical estimates, but the detailed dynamics of this 2D, strongly correlated, and far-from-equilibrium quantum system remain out of reach of current computational techniques. VL - 348 U4 - 540 - 544 UR - http://arxiv.org/abs/1411.7036v1 CP - 6234 J1 - Science U5 - 10.1126/science.aaa1385 ER -