Observation of spatial charge and spin correlations in the 2D Fermi-Hubbard model has been published in the Sept 16 edition of SCIENCE.  This is a result of work by physicists from MIT-Harvard Center for Ultracold Atoms, and Research Laboratory of Electronics, MIT, Department of Physics and Astronomy, San Jose State University, Instituto de Fisica Federal do Rio de Janeiro, Department of Physics The Pennsylvania State University and our own Prof Nandini Trivedi from OSU.  

 Strong electron correlations lie at the origin of high-temperature superconductivity. Its essence is believed to be captured by the Fermi-Hubbard model of repulsively interacting fermions on a lattice. Here we report on the site-resolved observation of charge and spin correlations in the two-dimensional (2D) Fermi-Hubbard model realized with ultracold atoms. Antiferromagnetic spin correlations are maximal at half-filling and weaken monotonically upon doping. At large doping, nearest-neighbor correlations between singly charged sites are negative, revealing the formation of a correlation hole, the suppressed probability of finding two fermions near each other. As the doping is reduced, the correlations become positive, signaling strong bunching of doublons and holes, in agreement with numerical calculations. The dynamics of the doublon-hole correlations should play an important role for transport in the Fermi-Hubbard model.

Read the full article.