Tunable multistability and nonuniform phases in a dimerized two-dimensional Rydberg lattice

We study the multistability of fixed points for a dimerized system of Rydberg atoms driven by two laser fields and trapped in a two-dimensional(2D)square lattice.For identical driving fields,the fixed points of this system exhibit stable uniform,unstable uniform,stable nonuniform,or oscillating nonuniform phases in the presence of a bistable region.For different driving fields,however,all(stable,unstable,or oscillating)phases become nonuniform instead,which then results in two islets isolated from the mainland of Rydberg excitation.We also show that a tristable region may stretch out from the(nonuniform)bistable region near the islets,indicating that a richer phase diagram can be attained by tuning the Rabi frequencies and/or detunings of the driving fields.Last but not least,the fixed points can adiabatically evolve from the islets to the mainland but can not inversely evolve from the mainland to the islets.