Observation of Josephson effect in ²³Na spinor Bose–Einstein condensates

The Josephson effect, an important quantum supercurrent phenomenon, has been extensively studied in superconductors and superfluids. In this paper, we investigate the rich physics of one-dimensional Josephson junctions in a red-detuned optical lattice with sodium (Na) quantum gas. A one-dimensional Josephson array is formed by setting up an optical lattice using a red-detuned laser. By characterizing the dependence of Josephson oscillations of the lattice depth, we experimentally demonstrate the Josephson current. The lattice depth is controlled by altering the lattice power, and our observations are consistent with theoretical predictions. These findings offer valuable insights into quantum coherent transport and the intricate dynamics inherent to superfluidity.