Speaker
Description
We present an atomtronic toolbox to study quantum transport phenomena and quantum scattering problems using Bose-Einstein condensates (BECs) in spatially and temporally modulated optical potentials. We have recently applied this apparatus to investigating atomic Josephson junctions.
Our platform can apply an arbitrary optical potential to a BEC, using a two-axis acousto-optical deflector and a digital micromirror device. To investigate atomtronic superconducting Josephson junctions, we form a tube-shaped BEC and introduce a movable repulsive barrier into the tube. The velocity of the barrier through the condensate and the chemical potential difference across the barrier are analogous to current and voltage, respectively. With an appropriate combination of AC and DC driving, the current-voltage curve of the device shows discrete Shapiro steps [1], that have previously been demonstrated in solid-state superconductors, and form the Josephson voltage standard. We investigate the microscopic origins of this behaviour by imaging density modulations in the condensate and comparing to numerical simulations. We demonstrate that Shapiro steps in our quantum gas platform are directly connected to phonon emission and vortex dynamics.
Additionally, we are developing a novel method for introducing an ultra-narrow barrier into the condensate. The “dark-state barrier” can achieve sub-wavelength widths using a pair of resonant Raman beams, with differing transverse modes, projected onto the atoms through an in-vacuum objective lens. The narrower barrier will allow for investigation of tunnelling phenomena, including probing the transition from weak-link transport to the tunnelling regime.
[1] E. Bernhart et al. Science 390, 1130-1133 (2025)
| I am the presenting author | Yes |
|---|