Conductor-Insulator Crossover in the Steady-State Ultracold Plasmas

We present a theoretical model of the ionization-recombination balance in the ultracold Rydberg gas-plasma mixture, which is caused by the collective processes rather than by individual interparticle interactions. This should be well relevant to the steady-state ultracold plasmas obtained in the recent experiment [B. Zelener, et al. Phys. Rev. Lett. 132, 115301 (2024)]. As follows from our calculations, there should be a sharp crossover from the insulating phase (Rydberg gas) to the conducting one (plasma) with increase in the particle density, which closely resembles Mott transition in the condensed-matter physics.