Stark modulated Rydberg dissipative time crystals at room temperature applied to sub-kHz electric field sensing

Out-of-equilibrium Rydberg gases exhibit emergent many-body phases due to mode competition. Sustained limit cycle oscillations (OSC) emerge when driven by B-fields at room temperature, forming robust Rydberg dissipative time crystals (DTC). Here we show that DC and AC Stark fields in the sub-kHz regime can be used to precisely shift (DC) or modulate (AC) the oscillation frequency of these DTCs, providing a powerful method for controllable time-domain dynamics in a room-temperature system. The AC Stark modulation induces frequency modulation (FM) of the OSC spectrum, enabling narrowband detection of extremely weak AC electric fields in the sub-kHz regime, with DC fields detected via Stark-induced shifts of the oscillation frequency. With a modest setup, a sensitivity of ~ 7.8µVcm^{- 1}Hz^{- 1/2} at 300 Hz is demonstrated - an ~ 8.7× improvement over state-of-art in the sub-kHz regime. Unlike on-resonant DTC sensing that is limited to operation close to the emergent limit cycle oscillations (10-15 kHz), the present approach is effective in the DC-600 Hz sub-kHz regime. This approach overcomes the size and bandwidth limitations of classical antennas at ultra-low frequencies and establishes a new class of ultra-compact (≪λ/10⁶) Rydberg-based electric-field sensors. These results open opportunities for compact extremely low-frequency (ELF) sensors in remote sensing, communications, geophysics, and biomedical diagnostics.