Experimental Suppression of Potential Roughness in an AC Zeeman Atom Chip Trap

We present experimental progress in demonstrating the suppression of atom chip potential roughness using a radiofrequency (RF) AC Zeeman trap for ultracold atoms. This work lays the foundation for developing a trapped atom interferometer based on spin-dependent AC Zeeman traps. One of the drawbacks of conventional atom chip traps based on DC magnetic fields is fragmentation of the ultracold atom cloud resulting from conductivity defects in the chip wires, known as potential roughness. This roughness can be a limiting factor in atom interferometry and strong 1D confinement experiments, for example. Our trapping scheme uses spin-dependent AC Zeeman potentials generated by sending RF (~20 MHz) currents through the atom chip wires. These currents generate circularly polarized magnetic fields to target transitions between sublevels within the hyperfine levels of rubidium-87. Previously, these AC trapping potentials have been theoretically shown to suppress atom chip roughness due to atomic transition selection rules. Here, we show qualitative evidence of roughness suppression using two-wire DC and AC Zeeman traps (same position and trap frequency). Furthermore, we present a design for a microwave atom chip that supports broadband RF and microwave fields for future atom interferometry experiments.