Frustrated magnets without geometrical frustration in bosonic flux ladders

We propose a scheme to realize a frustrated Bose-Hubbard model with ultracold atoms in an optical lattice that comprises the frustrated spin-1/2 quantum XX model. Our approach is based on a square ladder of magnetic flux similar to pi with one real and one synthetic spin dimension. Although this system does not have geometrical frustration, we show that at low energies it maps into an effective triangular ladder with staggered fluxes for specific values of the synthetic tunneling. We numerically investigate its rich phase diagram and show that it contains bond-ordered-wave and chiral superfluid phases. Our scheme gives access to minimal instances of frustrated magnets without the need for real geometrical frustration, in a setup of minimal experimental complexity.

Automated summary

We propose a scheme to realize a frustrated Bose-Hubbard model with ultracold atoms in an optical lattice that comprises the frustrated spin-1/2 quantum XX model. Our scheme utilizes a magnetic flux in a square ladder with one real and one synthetic spin dimension. Although this system does not have geometrical frustration, it can be mapped into an effective triangular ladder with staggered fluxes at low energies for specific values of synthetic tunneling. The scheme allows for minimal instances of frustrated magnets without the need for real geometrical frustration, in a setup of minimal experimental complexity.