Quantum Simulation of an FFLO Superconductor

超导性的发现是20世纪物理学的一个分水岭，激发了凝聚态物理的新领域，也使新技术成为可能。超导的本质是一些材料在冷却到临界温度以下时成为完美的导电体。Tc通常低于空气液化的温度。超导的机制还不完全清楚，我们也不知道Tc的上限。我们确实知道，携带电荷的粒子是电子对，它们通过各种有效的相互作用被弱束缚在一起。其中一种被提议的配对机制是“FFLO超导体”，以四位提议者的首字母缩写命名，其中的配对可以在强磁场的存在下存活下来。尽管进行了多次搜索，但FFLO超导体仍然难以捉摸。然而，它的存在将使物理学家更深入地了解超导的内部工作原理，并将开启新的应用，如超高速电子计算机和磁共振成像（MRI）。PI将使用量子模拟来实现FFLO超导体的模型，其中超冷原子代替电子，电子在由光驻波构成的周期性晶格中运动。这种类型的量子模拟忠实地实现了FFLO超导体的模型，并将使PI和学生能够测试理论预测。预计将有几名学生在PI的项目中获得博士学位，其中一些人可能会在创新型初创公司就业，贡献他们的专业知识，开发量子计算的新技术。超导性和磁性是电子材料中常见的物质相，它们不能共存。如果库珀对获得有限的质心动量，而不是像超导的标准理论那样形成零动量对，那么FFLO超导体可以适应共存的磁场。人们认为FFLO在低维（准一维或二维）中最受青睐。到目前为止，还没有直接的证据证明有限动量库珀对的存在。PI将通过模拟实际的电子材料在磁场作用下的FFLO状态（具有有限动量配对）是否是物质的合法相来解决问题，其中自旋不平衡的原子费米气体被限制在使用二维光学晶格形成的一维波导的二维阵列中。晶格势弱到足以使相邻波导中的原子通过隧道耦合相互作用。由此产生的域壁，即FFLO状态的最终签名，将直接成像。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The discovery of superconductivity was a watershed moment in 20th century physics, sparking the new field of condensed matter physics, as well as enabling new technologies. The essence of superconductivity is that some materials become perfect conductors of electricity when cooled below a critical temperature Tc. Tc is typically below the temperature where air liquifies. The mechanisms that underlie superconductivity are not fully known, nor do we know the upper limit of Tc. We do know that the charge-carrying particles are pairs of electrons that are weakly bound to each other by various effective interactions. One of the proposed pairing mechanisms is the “FFLO superconductor,” named after the initials of the four proposers, in which the pairs may survive the presence of a strong magnetic field. Despite many searches, the FFLO superconductor remains elusive. Its existence, however, would give physicists more insight into the inner workings of superconductivity and it would unlock new applications, such as ultra-fast electronic computers and magnetic resonance imaging (MRI). The PI will use quantum simulation to realize a model of the FFLO superconductor, for which ultra-cold atoms stand-in for the electrons, which move in a periodic crystal lattice made from standing waves of light. This type of quantum simulation faithfully realizes a model of the FFLO superconductor and will enable the PI and students to test the theoretical predictions. Several students are expected to earn PhD degrees working on this project with the PI, and likely some of these will gain employment at innovative start-up companies contributing their expertise to develop new technologies for quantum computation.Superconductivity and magnetism are phases of matter commonly found in electronic materials that do not coexist. The FFLO superconductor may adapt to a co-existing magnetic field if the Cooper pairs acquire a finite center-of-mass momentum rather than forming zero momentum pairs as in the standard theory of superconductivity. It is believed that FFLO is most favored in low-dimensions, either in quasi-1D or 2D. As of yet, there is no direct evidence for finite momentum Cooper pairs. The PI will resolve whether the FFLO state, with finite-momentum pairing, is a legitimate phase of matter by simulating the actual electronic materials subjected to a magnetic field, with a spin-imbalanced atomic Fermi gas confined to a two-dimensional array of one-dimensional waveguides formed using a 2D optical lattice. The lattice potential is weak enough that atoms in adjacent waveguides interact via tunnel coupling. The resulting domain walls, the definitive signature of the FFLO state, will be directly imaged.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.