Observation of emergent scaling of spin-charge correlations at the onset of the pseudogap

TL;DR

This study uses a quantum simulator to observe universal scaling in spin-charge correlations near the pseudogap in cuprate-like materials, revealing new magnetic behaviors and a temperature scale linked to the pseudogap.

Contribution

It provides the first experimental observation of universal scaling in spin-charge correlations in a Fermi-Hubbard system near the pseudogap regime.

Findings

Discovered a doping-dependent universal scaling behavior in correlations.

Identified a temperature scale comparable to the pseudogap temperature T*.

Revealed qualitative changes in magnetic properties at the pseudogap onset.

Abstract

In strongly correlated materials, interacting electrons are entangled and form collective quantum states, resulting in rich low-temperature phase diagrams. Notable examples include cuprate superconductors, in which superconductivity emerges at low doping out of an unusual "pseudogap" metallic state above the critical temperature. The Fermi-Hubbard model, describing a wide range of phenomena associated with strong electron correlations, still offers major computational challenges despite its simple formulation. In this context, ultracold atoms quantum simulators have provided invaluable insights into the microscopic nature of correlated quantum states. Here, we use a quantum gas microscope Fermi-Hubbard simulator to explore a wide range of dopings and temperatures in a regime where a pseudogap is known to develop. By measuring multi-point correlation functions up to fifth order, we uncover a novel universal scaling behaviour in magnetic and higher-order spin-charge correlations characterised by a doping-dependent temperature scale. Accurate comparisons with determinant Quantum Monte Carlo and Minimally Entangled Typical Thermal States simulations confirm that this temperature scale is comparable to the pseudogap temperature T*. Our quantitative findings reveal a novel qualitative behaviour of magnetic properties and spin-charge correlations in an emergent pseudogap and pave the way towards the exploration of charge pairing and collective phenomena expected at lower temperatures.