Spin-Twisted Optical Lattices: Tunable Flat Bands and Larkin-Ovchinnikov Superfluids

Moire superlattices in twisted bilayer graphene and transition-metal dichalcogenides have emerged as a powerful tool for engineering novel band structures and quantum phases of two-dimensional quantum materials. Here we investigate Moir ' e physics emerging from twisting two independent hexagonal optical lattices of atomic (pseudo-)spin states (instead of bilayers) that exhibit remarkably different physics from twisted bilayer graphene. We employ a momentum-space tight-binding calculation that includes all range real-space tunnelings and show that all twist angles theta less than or similar to 6 degrees can become magic and support gapped flat bands. Because of the greatly enhanced density of states near the flat bands, the system can be driven to superfluidity by weak attractive interaction. Strikingly, the superfluid phase corresponds to a Larkin-Ovchinnikov state with finite momentum pairing that results from the interplay between flat bands and interspin interactions in the unique single-layer spin-twisted lattice. Our work may pave the way for exploring novel quantum phases and twistronics in cold atomic systems.

Automated summary

The study explores the Moiré physics emerging from twisting two independent hexagonal optical lattices of atomic spin states, showing potential for magic twist angles to support gapped flat bands. Enhanced density of states near the flat bands can lead to superfluidity driven by weak attractive interactions, with the superfluid phase corresponding to a Larkin-Ovchinnikov state with finite momentum pairing. This work may lead to novel quantum phases and twistronics in cold atomic systems.