Produced the first AC atomtronics circuit in the LENS laboratory of strongly correlated Fermi systems (Li-Lab)
Sat, 20 Dec 2025, 07:42 a.m.
The experimental team led by Dr. Giacomo Roati has realized the first AC current in a strongly-interacting atomic Josephson junction, an atomtronic device composed by two reservoirs of ultracold atoms of lithium-6 separated by a thin repulsive barrier generated with laser light. By translating the barrier with an oscillatory motion, the team introduced an AC current of controlled frequency in the circuit and observed the characteristic Shapiro steps in the current-voltage curve. In fact, when AC driven, the junction develops a number of voltage plateaus, whose height is an integer multiple of the current oscillation frequency, that in superconducting junctions provide the standard for the metrological definition of the voltage. The atomtronic AC-driven Josephson junction allowed the LENS team to observe the microscopic dynamics underneath the phenomenon of the Shapiro steps with expanded resolution, thanks to the relatively slower time scales of the atomic system dynamics with respect to the superconducting one. The results, recently published in Science, highlights how the Shapiro steps arise from the synchronization of the junction phase with the external drive, leading to the periodic emission of vortex-antivortex pairs.
- Giulia Del Pace et al. Shapiro steps in strongly-interacting Fermi gases.Science390,1125-1129(
2025).DOI:10.1126/science. ads8885
Giulia Del Pace