Optical lattice for tripod-like atomic level structure

TL;DR

This paper extends optical lattice techniques to a four-level tripod atomic system, creating a stable, spin-like dark space with tunable hopping and interactions, enabling exploration of complex quantum phenomena.

Contribution

It introduces a novel four-level tripod scheme for optical lattices, enhancing stability and control over atomic motion and interactions compared to previous three-level systems.

Findings

Dark subspace lifetime is up to 100 times longer than in Λ systems.

Lattices with adjustable hopping rates J1, J2, J3 are achievable.

New inter-site interactions not possible in standard optical lattices.

Abstract

Standard optical potentials use off-resonant laser standing wave induced AC-Stark shift. In a recent development [Phys. Rev. Lett. {\bf 117}, 233001 (2016)] a three-level scheme in $\Lambda$ configuration coupled coherently by resonant laser fields was introduced leading to an effective lattice with subwavelength potential peaks. Here as an extension of that work to a four level atomic setup in the tripod configuration is used to create spin $1/2$-like two-dimensional dark-space with 1D motion and the presence of external gauge fields. Most interestingly for a possible application, the lifetime for a dark subspace motion is up to two orders of magnitude larger than for a similar $\Lambda$ system. The model is quite flexible leading to lattices with significant nearest, next-nearest, or next-next-nearest hopping rates, $J_1,J_2,J_3$ opening up new intriguing possibilities to study, e.g. frustrated systems. The characteristic Wannier functions lead also to new type of inter-site interactions not realizable in typical optical lattices.