Unconventional Phases of Attractive Fermi Gases in Synthetic Hall Ribbons

An innovative way to produce quantum Hall ribbons in a cold atomic system is to use M hyperfine states of atoms in a one-dimensional optical lattice to mimic an additional “synthetic dimension.” A notable aspect here is that the SU(M) symmetric interaction between atoms manifests as “infinite ranged” along the synthetic dimension. We study the many-body physics of fermions with SU(M) symmetric attractive interactions in this system using a combination of analytical field-theoretic and numerical density-matrix renormalization-group methods. We uncover the rich ground-state phase diagram of the system, including unconventional phases such as squished baryon fluids, shedding light on many-body physics in low dimensions. Remarkably, changing the parameters entails interesting crossovers and transition; e.g., we show that increasing the magnetic field (that produces the Hall effect) converts a “ferrometallic” state at low fields to a “squished baryon superfluid” (with algebraic pairing correlations) at high fields. We also show that this system provides a unique opportunity to study quantum phase separation in a multi flavor ultracold fermionic system.