Ultrafast many-body dynamics of dense Rydberg gases and ultracold plasma

Abstract

Understanding Coulomb driven many-body dynamics in ultracold atomic systems far from equilibrium remains an open challenge, particularly when ultrafast excitation channels create competing pathways toward Rydberg gases or ultracold plasmas. Here, we investigate the many-body dynamics in a ${}^{87}$Rb Bose-Einstein condensate after exposure to a single femtosecond laser pulse. By tuning the laser wavelength across the two-photon ionization threshold, we can control the initial state that is either dominated by free electrons and leads to an ultracold plasma or dominated by electrons in excited states which leads to a dense Rydberg gas. The large bandwidth enables overcoming the Rydberg blockade that limits the excitation density for narrow-linewidth lasers. We directly measure the kinetic energy of the released electrons and compare the final distribution of free, bound and plasma electrons to molecular dynamics simulations where the electrons are modeled as individual particles including collisional ionization and recombination processes. We find very good agreement between the simulated electron distribution and the experimental observation. We identify charge imbalance as main driver for the decay of a dense Rydberg gas into an ultracold plasma.

10 pages, 8 figures

References in corpus (9)

• Ultracold Neutral Plasmas
• Ultrafast energy exchange between two single Rydberg atoms on the nanosecond timescale
• Complete photoionization experiments via ultra-fast coherent control with polarization-multiplexing
• Ultrafast Electron Cooling in an Expanding Ultracold Plasma
• Photoionization of Rydberg Atoms in Optical Lattices
• Ultra-large Rydberg dimers in optical lattices
• Simulations of prompt many-body ionization in a frozen Rydberg gas
• Shaped free electron vortices
• Generation of 480 nm picosecond pulses for ultrafast excitation of Rydberg atoms