Observation of discrete time quasicrystal in Rydberg atomic gases.

Abstract

Discrete time quasicrystals (DTQC) constitute a class of non-equilibrium matter characterized by temporal order without strict periodicity, in contrast to conventional time crystals. Investigating these phenomena is essential for expanding our fundamental understanding of far-from-equilibrium quantum matter and spontaneous symmetry breaking beyond periodic regimes. Here, we experimentally observe a DTQC in a driven-dissipative ensemble of strongly interacting Rydberg atoms, displaying non-equilibrium dynamical response with a different finite Abelian group symmetry <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>Z</mi></mrow> <mrow><mi>m</mi></mrow> </msub> <mo>×</mo> <msub><mrow><mi>Z</mi></mrow> <mrow><mi>n</mi></mrow> </msub> </math> . By applying a quasiperiodic drive using a dual-frequency drive with incommensurate frequencies, we demonstrate that the system exhibits a robust subharmonic response at multiple incommensurate frequencies, signifying the emergence of a DTQC phase. We map the full phase diagram of the system, which includes the DTQC phase, and demonstrate its rigidity against perturbations in both RF field intensity and laser detuning. Moreover, we observe a cyclic group symmetry effect that constrains the construction of <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>Z</mi></mrow> <mrow><mn>2</mn></mrow> </msub> <mo>×</mo> <msub><mrow><mi>Z</mi></mrow> <mrow><mn>3</mn></mrow> </msub> </math> -symmetric DTQC. This work establishes a versatile platform for studying non-equilibrium phases of matter and provides insights into the dynamics of time-translation symmetry breaking in quantum many-body systems.