Observation of Spatial Charge and Spin Correlations in the 2D Fermi-Hubbard Model
Abstract
Strong electron correlations lie at the origin of transformative phenomena such as colossal magneto-resistance and high-temperature superconductivity. Already near room temperature, doped copper oxide materials display remarkable features such as a pseudo-gap and a "strange metal" phase with unusual transport properties. The essence of this physics is believed to be captured by the Fermi-Hubbard model of repulsively interacting, itinerant 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. Correlations between singly charged sites are negative at large doping, revealing the Pauli and correlation hole\textemdash a suppressed probability of finding two fermions near each other. However, as the doping is reduced below a critical value, correlations between such local magnetic moments become positive, signaling strong bunching of doublons and holes. Excellent agreement with numerical linked-cluster expansion (NLCE) and determinantal quantum Monte Carlo (DQMC) calculations is found. Positive non-local moment correlations directly imply potential energy fluctuations due to doublon-hole pairs, which should play an important role for transport in the Fermi-Hubbard model.
Keywords
Cite
@article{arxiv.1606.04089,
title = {Observation of Spatial Charge and Spin Correlations in the 2D Fermi-Hubbard Model},
author = {Lawrence W. Cheuk and Matthew A. Nichols and Katherine R. Lawrence and Melih Okan and Hao Zhang and Ehsan Khatami and Nandini Trivedi and Thereza Paiva and Marcos Rigol and Martin W. Zwierlein},
journal= {arXiv preprint arXiv:1606.04089},
year = {2016}
}