2019/01/31 by Minjae Jo, Jaegon Um, B. Kahng
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Condensed matter physics #Excited state #Opinion Dynamics and Social Influence #Phase (matter) #Phase diagram #Phase transition #Physics #Quantum #Quantum critical point #Quantum many-body systems #Quantum mechanics #Quantum phase transition #Quantum phases #Renormalization group #Rydberg atom #Rydberg formula #Tricritical point #cond-mat.stat-mech
paper · pdf · doi:10.1103/physreve.99.032131
published as Phys. Rev. E 99, 032131 (2019) · 10 pages, 2 figures
arxiv created 2019/03/16 · openalex publication_date 2019/03/26 · arxiv updated 2019/04/03 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We investigate a nonequilibrium phase transition in a dissipative and coherent quantum spin system using the quantum Langevin equation and mean-field theory. Recently, the quantum contact process (QCP) was theoretically investigated using the Rydberg antiblockade effect, in particular, when the Rydberg atoms were excited in s states so that their interactions were regarded as being between the nearest neighbors. However, when the atoms are excited to d states, the dipole-dipole interactions become effective, and long-range interactions must be considered. Here we consider a quantum spin model with a long-range QCP, where the branching and coagulation processes are allowed not only for the nearest-neighbor pairs but also for long-distance pairs, coherently and incoherently. Using the semiclassical approach, we show that the mean-field phase diagram of our long-range model is similar to that of the nearest-neighbor QCP, where the continuous (discontinuous) transition is found in the weak (strong) quantum regime. However, at the tricritical point, we find a new universality class, which was neither that of the QCP at the tricritical point nor that of the classical directed percolation model with long-range interactions. Implementation of the long-range QCP using interacting cold gases is discussed.