Scientific Results

Experimental signatures of an absorbing-state phase transition in an open driven many-body quantum system

Year: 2107

Authors: Morsch O., R. Gutierrez, C. Simonelli, M. Archimi, F. Castellucci, E. Arimondo, D. Ciampini, M. Marcuzzi, I. Lesanovsky,

Autors Affiliation: [ 1 ]‎ Univ Nottingham, Sch Phys & Astron, Nottingham NG7 2RD, England
[ 2 ]‎ Univ Nottingham, Ctr Math & Theoret Phys Quantum Nonequilibrium Sy, Nottingham NG7 2RD, England
[ 3 ]‎ Univ Rey Juan Carlos, Complex Syst Grp, Madrid 28933, Spain
[ 4 ]‎ INO CNR, Via G Moruzzi 1, I-56124 Pisa, Italy
[ 5 ]‎ Univ Pisa, Dipartimento Fis E Fermi, Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy
[ 6 ]‎ Univ Pisa, Dipartimento Fis E Fermi, CNISM UdR, Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy

Abstract: 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.

Journal/Review: PHYSICAL REVIEW A – ATOMIC, MOLECULAR, AND OPTICAL PHYSICS

Volume: 96      Pages from: 041602  to: 041602

KeyWords: Rydberg atoms; percolation; contact process
DOI: 10.1103/PhysRevA.96.041602