Large-Amplitude Superexchange of High-Spin Fermions in Optical Lattices

TL;DR

This paper demonstrates how high-spin fermionic systems in optical lattices can exhibit large-amplitude superexchange processes, revealing new regimes of spin fluctuations and tunneling mechanisms with potential experimental realizations.

Contribution

It introduces a novel superexchange regime driven by tunneling-energy gaps in shallow potentials, expanding understanding of spin dynamics in high-spin fermionic systems.

Findings

Identification of a superexchange dominated regime at weak interactions.

Discovery of a crossover between negligible and strong spin fluctuation regimes.

Proposal for experimental observation with ultracold 40K atoms.

Abstract

We show that fermionic high-spin systems with spin-changing collisions allow to monitor superexchange processes in optical superlattices with large amplitudes and strong spin fluctuations. By investigating the non-equilibrium dynamics, we find a superexchange dominated regime at weak interactions. The underlying mechanism is driven by an emerging tunneling-energy gap in shallow few-well potentials. As a consequence, the interaction-energy gap that is expected to occur only for strong interactions in deep lattices is reestablished. By tuning the optical lattice depth, a crossover between two regimes with negligible particle number fluctuations is found: first, the common regime with vanishing spin-fluctuations in deep lattices and, second, a novel regime with strong spin fluctuations in shallow lattices. We discuss the possible experimental realization with ultracold 40K atoms and observable quantities in double wells and two-dimensional plaquettes.