Disorder and Dynamics in Strongly Correlated Optical Lattices

我们正在开展两个项目，将推进无序量子气体的最新技术，从而为解决与凝聚态物理和材料科学相关的悬而未决的问题提供新的方法。首先，我们正在开发一种技术来直接测量被困在三维无序光学晶格中的超冷气体的可压缩性。我们将应用这种方法来确定我们发现的无序诱导绝缘体的性质，这可能是第一次使用原子明确地检测玻色玻璃相。其次，我们在无序费米气体装置中增加了一个立方光学晶格，首次实现了使用超冷原子的无序费米-哈伯德模型。在这些实验中，利用激光和磁场的结合将被捕获的原子气体冷却到纳米开尔文的温度。通过缓慢打开三对反向传播的红外晶格激光束和绿色光学散斑场，将无序光学晶格叠加在气体上。通过调节激光强度，可以平滑地调整材料参数的等效量，如无序强度和隧道能量。为了测量可压缩性，将两束激光（在电子跃迁附近调谐）应用于铷-87气体，当限制阱改变时，将只对位于无序晶格中间的原子成像。为了给费米子钾-40原子创造一个无序晶格，额外的晶格激光束将被应用到超冷气体中。我们将测量施加力时气体的速度，以便在无序晶格中寻找预测的金属-绝缘体跃迁。无序和强相互作用的相互作用是凝聚态物理中一个关键的突出问题。基本问题集中在无序和相互作用如何合作或竞争以创造平衡中的局域相以及无序对动力学性质的影响。无序对量子材料的影响对于技术应用也是至关重要的。从我们的实验中获得的见解可能会导致具有对能源应用至关重要的最高性能的材料的改进，例如高温超导铜酸盐。加深对无序和相互作用如何影响材料特性的理解也可能使强相关材料在热电发电等功能中的新应用成为可能。

We are carrying out two projects that will advance the state-of-the-art for disordered quantum gases, thus enabling new methods for attacking outstanding questions related to condensed matter physics and materials science. First, we are developing a technique to directly measure compressibility for ultra-cold gases trapped in 3D disordered optical lattices. We will apply this method to identify the nature of a disorder-induced insulator that we discovered, potentially detecting a Bose-glass phase using atoms unambiguously for the first time. Second, we are adding a cubic optical lattice to our disordered Fermi gas apparatus to achieve the first realization of the disordered Fermi-Hubbard model using ultra-cold atoms. In these experiments, trapped atom gases are cooled to nanoKelvin temperatures using a combination of lasers and magnetic fields. A disordered optical lattice is superimposed on the gas by slowly turning on three pairs of counter-propagating infrared lattice laser beams and a green optical speckle field. The equivalent of material parameters, such as the disorder strength and tunneling energy, are smoothly tuned by adjusting the laser intensities. To measure compressibility, two laser beams (tuned near an electronic transition) applied to a Rubdium-87 gas will be used to image only the atoms located in the middle of the disordered lattice as the confining trap is changed. To create a disordered lattice for fermionic Potassium-40 atoms, additional lattice laser beams will be applied to an ultra-cold gas. We will measure the velocity of the gas as a force is applied in order to search for a predicted metal-insulator transition in the disordered lattice.The interplay of disorder and strong interactions is one of the key outstanding problems in condensed matter physics. Fundamental questions center on how disorder and interactions either cooperate or compete to create localized phases in equilibrium and the influence of disorder on dynamical properties. The impact of disorder on quantum materials is also of prime importance to technological applications. Insight gained from our experiments may lead to improvements in materials with superlative properties that are important to energy applications, such as the high-temperature superconducting cuprates. Enhanced understanding of how disorder and interactions influence material properties may also enable new applications for strongly correlated materials in functions such as thermoelectric power generation.