Quantum dynamics of a mobile spin impurity

TLDR: In this article, the spatial probability distribution of the impurity at different times using single-site-resolved imaging of bosonic atoms in an optical lattice was investigated, showing evidence of polaronic behaviour.

Abstract: One of the elementary processes in quantum magnetism is the propagation of spin excitations. Here we study the quantum dynamics of a deterministically created spin-impurity atom, as it propagates in a one-dimensional lattice system. We probe the spatial probability distribution of the impurity at different times using single-site-resolved imaging of bosonic atoms in an optical lattice. In the Mott-insulating regime, the quantum-coherent propagation of a magnetic excitation in the Heisenberg model can be observed using a post-selection technique. Extending the study to the superfluid regime of the bath, we quantitatively determine how the bath affects the motion of the impurity, showing evidence of polaronic behaviour. The experimental data agree with theoretical predictions, allowing us to determine the effect of temperature on the impurity motion. Our results provide a new approach to studying quantum magnetism, mobile impurities in quantum fluids and polarons in lattice systems.

Figures

Figure 3. Effect of thermal excitations on the coherent spin dynamics. Shown are position distributions of the spin impurity for J/U = 0.053 and a hold time of 40ms, a generated from positive images (blue bars) and b after post-selection from negative images containing one empty site in the chain (green bars). c, Position distributions from tDMRG simulations for different temperatures. d, Contrast of the simulated distributions (open circles) and propagation velocity (gray filled circles) as a function of the temperature T . The blue and green filled circles show the contrast extracted from the experimental data of a and b, respectively. Error bars denote the 1σ uncertainty.