A cold-atom Fermi-Hubbard antiferromagnet
A cold-atom Fermi-Hubbard antiferromagnet
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DOI：
10.1038/nature22362
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发表时间：
2017-05-25
期刊：
影响因子：
64.8
通讯作者：
Greiner, Markus
中科院分区：
文献类型：
--
作者：
Azurenko, Anton M.;Chiu, Christie S.;Greiner, Markus
具有强关联电子的系统中的奇异现象来自自旋和运动自由度之间的相互作用。例如，掺杂反铁磁体预计会产生伪隙状态和高温超导体(1)。在光学晶格中使用超冷费米子的量子模拟(2-8)可以帮助回答有关掺杂哈密顿量(9-14)的公开问题，最近量子气体显微镜(15-20)提出了这一问题。本文报道了反铁磁体在排斥相互作用费米气体中以0.25倍的隧穿能量在二维方晶格上的实现。反铁磁长程有序通过关联长度的发散、自旋结构因子峰值的发展和接近基态值的交错磁化来表现。我们将系统从半填充状态转变为复杂的多体状态，并发现在反铁磁有序矢量处存在强的磁关联，直到掺杂约15%。在这种情况下，数值模拟具有挑战性，因此实验提供了一个有价值的基准。我们的结果表明，光学晶格中冷原子的显微镜可以帮助我们理解低温费米-哈伯德模型。
Exotic phenomena in systems with strongly correlated electrons emerge from the interplay between spin and motional degrees of freedom. For example, doping an antiferromagnet is expected to give rise to pseudogap states and high-temperature superconductors(1). Quantum simulation(2-8) using ultracold fermions in optical lattices could help to answer open questions about the doped Hubbard Hamiltonian(9-14), and has recently been advanced by quantum gas microscopy(15-20). Here we report the realization of an antiferromagnet in a repulsively interacting Fermi gas on a two-dimensional square lattice of about 80 sites at a temperature of 0.25 times the tunnelling energy. The antiferromagnetic long-range order manifests through the divergence of the correlation length, which reaches the size of the system, the development of a peak in the spin structure factor and a staggered magnetization that is close to the ground-state value. We hole-dope the system away from half-filling, towards a regime in which complex many-body states are expected, and find that strong magnetic correlations persist at the antiferromagnetic ordering vector up to dopings of about 15 per cent. In this regime, numerical simulations are challenging(21) and so experiments provide a valuable benchmark. Our results demonstrate that microscopy of cold atoms in optical lattices can help us to understand the low-temperature Fermi-Hubbard model.