2016/11/30 by Ricardo Gutierrez, Ricardo Gutiérrez, Cristiano Simonelli +10 · 3 citations
Physics and Astronomy · #Atomic physics #Cold Atom Physics and Bose-Einstein Condensates #Excitation #Excited state #Ionization #Non-equilibrium thermodynamics #Phase transition #Physics #Population #Quantum #Quantum critical point #Quantum mechanics #Quantum phase transition #Quantum, superfluid, helium dynamics #Rydberg formula #Spectroscopy and Quantum Chemical Studies #cond-mat.stat-mech #physics.atom-ph #quant-ph
paper · pdf · doi:10.1103/physreva.96.041602
published as Phys. Rev. A 96, 041602 (2017) · 14 pages, 8 figures
openalex created_date 2017/01/06 · openalex publication_date 2017/10/09 · arxiv created 2017/10/10 · arxiv updated 2017/10/18 · openalex updated_date 2026/08/05
Understanding and probing phase transitions in nonequilibrium systems is an ongoing challenge in physics. A particular instance are phase transitions that occur between a nonfluctuating absorbing phase, e.g., an extinct population, and one in which the relevant order parameter, such as the population density, assumes a finite value. Here, we report the observation of signatures of such a nonequilibrium phase transition in an open driven quantum system. In our experiment, rubidium atoms in a quasi-one-dimensional cold disordered gas are laser excited to Rydberg states under so-called facilitation conditions. This conditional excitation process competes with spontaneous decay and leads to a crossover between a stationary state with no excitations and one with a finite number of excitations. We relate the underlying physics to that of an absorbing-state phase transition in the presence of a field (i.e., off-resonant excitation processes) which slightly offsets the system from criticality. We observe a characteristic power-law scaling of the Rydberg excitation density as well as increased fluctuations close to the transition point. Furthermore, we argue that the observed transition relies on the presence of atomic motion which introduces annealed disorder into the system and enables the formation of long-ranged correlations. Our study paves the road for future investigations into the largely unexplored physics of nonequilibrium phase transitions in open many-body quantum systems.