Spin- and density-resolved microscopy of antiferromagnetic correlations in Fermi-Hubbard chains

Abstract

The repulsive Hubbard Hamiltonian is one of the foundational models describing strongly correlated electrons and is believed to capture essential aspects of high-temperature superconductivity. Ultracold fermions in optical lattices allow for the simulation of the Hubbard Hamiltonian with control over kinetic energy, interactions, and doping. A great challenge is to reach the required low entropy and to observe antiferromagnetic spin correlations beyond nearest neighbors, for which quantum gas microscopes are ideal. Here, we report on the direct, single-site resolved detection of antiferromagnetic correlations extending up to three sites in spin-1/2 Hubbard chains, which requires entropies per particle well below s* = ln(2). The simultaneous detection of spin and density opens the route toward the study of the interplay between magnetic ordering and doping in various dimensions.

Quantum simulation of a Fermi–Hubbard model using a semiconductor quantum dot array

“…Seminal efforts are underway in the control of artificial quantum systems, that can be made to emulate the underlying Fermi-Hubbard models [5, 6, 7, 8,9,10,11]. Electrostatically confined conduction band electrons define interacting quantum coherent spin and charge degrees of freedom that allow all-electrical pure-state initialisation and readily adhere to an engineerable Fermi-Hubbard Hamiltonian [12,13,14,15,16,17,18,19,20,21,22,23].…”

“…Although the potential of such correlated-electron phases for realizing novel electronic and magnetic properties has prompted quantum simulation efforts across multiple platforms [5,6,7,8,9,10,24,25], experimental correlations are often limited in span and strength due to the residual entropy of the initialized system [8,9,10]. Furthermore, scaling to similarly homogeneous but larger system sizes is not always straightforward [5,7,8,9,10,11,25]. Semiconductor quantum dots form a scalable platform that is naturally described by a Fermi-Hubbard model in the low-temperature, strong-interaction regime, when cooled down to dilution temperatures [12,13,15,14,16].…”

A cold-atom Fermi–Hubbard antiferromagnet

“…Already, Mott-insulating phases and short-range antiferromagnetic correlations have been observed, but temperatures were too high to create an antiferromagnet [12][13][14][15]. A new perspective is afforded by quantum gas microscopy [16][17][18][19][20][21][22][23][24][25][26][27][28], which allows readout of magnetic correlations at the site-resolved level [25][26][27][28]. Here we report the realization of an antiferromagnet in a repulsively interacting Fermi gas on a 2D square lattice of approximately 80 sites.…”

Dynamical mean-field theory study of stripe order and d -wave superconductivity in the two-dimensional Hubbard model

“…Experimental methods for realizing the Hubbard Hamiltonian have also been developed in the ultracold gas community [3][4][5]. Especially, the recent development of the fermionic quantum gas microscopes provides an interesting platform for observing magnetic order [6][7][8][9][10][11][12][13][14][15], although further advances are needed to reach the possible superconducting phases.…”