Observation of Spatial Charge and Spin Correlations in the 2D Fermi-Hubbard Model

Lawrence W. Cheuk; Matthew A. Nichols; Katherine R. Lawrence; Melih Okan; Hao Zhang; Ehsan Khatami; Nandini Trivedi; Thereza Paiva; Marcos Rigol; Martin W. Zwierlein

doi:10.1126/science.aag3349

arXiv · 1606.04089

Observation of Spatial Charge and Spin Correlations in the 2D Fermi-Hubbard Model

Lawrence W. Cheuk·Matthew A. Nichols·Katherine R. Lawrence·Melih Okan·Hao Zhang·Ehsan Khatami·Nandini Trivedi·Thereza Paiva·Marcos Rigol·Martin W. Zwierlein

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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.

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BibTeX RIS

Lawrence W. Cheuk, Matthew A. Nichols, Katherine R. Lawrence, Melih Okan, Hao Zhang, Ehsan Khatami, Nandini Trivedi, Thereza Paiva, Marcos Rigol, Martin W. Zwierlein. 2016-06-13. Observation of Spatial Charge and Spin Correlations in the 2D Fermi-Hubbard Model. https://doi.org/10.1126/science.aag3349

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