Imaging and Probing Spin Polarons in Kinetically Frustrated Lattices

Kinetically frustrated lattices, even in the absence of superexchange interactions, are predicted to have magnetism appear in the form of itinerant spin polarons — bound states of magnons and charge dopants. Although signatures of this kinetic magnetism have recently been observed in doped van der Waals heterostructures, a microscopic observation is still lacking. Here, we present new results directly imaging itinerant spin polarons in a triangular lattice Hubbard system using a quantum gas microscope, where full spin-charge readout allows measurement of arbitrary n-point correlation functions. Around a hole dopant, we see enhanced antiferromagnetic spin correlations. Furthermore, we see enhanced ferromagnetic correlations in the presence of a charge dopant, a manifestation of the Nagaoka effect. We study the evolution of these correlations with density and interaction, and are able to use 4-point correlations to show the relative contributions of the kinetic and superexchange magnetisms. The robustness of kinetic magnetism at experimental temperatures allows for the exploration of potential mechanisms of hole pairing and superconductivity in frustrated systems. Additionally, we may be able to directly measure the binding energy of itinerant spin polarons in frustrated systems using Raman spectroscopy.