Inhomogeneity and Charge Modulation in Unconventional Superconductors

摘要在科技日益发达的当今世界，量子材料是新型电子器件的未来。用于核磁共振成像（MRI）的超导体是成熟的技术，用于量子计算的量子比特是新生的技术，这是在我们的社会中无处不在的量子材料的两个例子。这项研究是为了更好地了解目前使用的功能量子材料，以便发现下一代量子材料而做出的巨大努力的一部分。该项目将专注于超导材料，用于核磁共振成像和量子计算。使用世界上最高磁场的先进实验技术、脉冲电源系统和射频系统等技术也可以推动能源、通信和制造业等部门的发展。最后，参与这些项目的本科生和研究生将被培养为下一代科学家。摘要理解量子力学基态对于创造下一代电子器件和发展量子通信至关重要。PI的研究通过对显示非均匀超导特征的准二维有机超导体进行系统测量，推进了对量子系统的理解。这种奇异的超导状态是一种空间调制超导有序参数和不成对电子磁晶格的可调谐混合物，在50多年前就被预测到，被称为FFLO状态。FFLO状态可以通过温度、磁场的方向和强度以及压力进行高度可调。本研究继续使用隧道二极管振荡器和有机和镍超导体的比热进行射频穿透深度的核心测量。PI还使用x射线测量FFLO状态下电荷调制的对称性和波长，以及电荷密度波。为了促进这些实验，PI正在与阿贡国家实验室（APS）的先进光子源以及塔拉哈西和洛斯阿拉莫斯的国家高磁场实验室合作，升级APS的高磁场访问。在有机导体和粒子导体中，阴离子或元素取代和适中的压力使得很容易穿越超导材料中普遍存在的温度-载流子浓度相图。调整系统从密度波绝缘状态，通过超导，进入金属状态，将提供量子临界点被认为是负责超导的证据。理解基态之间的竞争是量子材料的一个核心问题，而量子临界点是这个问题的核心。测量、模型计算和广泛的晶体样品库的结合将进一步实现理解量子材料物理的目标。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。

Non-Technical AbstractQuantum materials are the future of new electronic devices in our increasingly technological world. Superconductors for MRI medical imaging, a mature technology, and qubits for quantum computing, a nascent technology, are two examples of quantum materials that are or will be ubiquitous in our society. This research is part of a large effort to better understand the functional quantum materials used presently so that the next generation of quantum materials can be discovered. This project will focus on superconducting materials, used both in MRI imaging and quantum computing. Advancing experimental techniques that use the highest magnetic fields available in the world, pulsed power systems, and radio frequency systems are some of the technologies that also can advance sectors such as energy, communications, and manufacturing. Finally, the undergraduate, and graduate students who participate in these projects are trained as the next generation of scientists. Technical AbstractUnderstanding quantum mechanical ground states is essential to create the next generation of electronic devices and develop quantum communications. The PI's research is advancing the understanding of quantum systems by making systematic measurements of quasi-two dimensional organic superconductors that show signatures of inhomogeneous superconductivity. This exotic superconducting state, a tunable mixture of a spatially modulated superconducting order parameter and a magnetic lattice of unpaired electrons, was predicted over 50 years ago, and is called the FFLO state. The FFLO state is highly tunable via temperature, the direction and strength of the magnetic field, and pressure. This research continues the core measurements of rf penetration depth using a tunnel diode oscillator and specific heat of organic and pnictide superconductors. The PI also measures the symmetry and wavelength of the charge modulation in the FFLO state and charge density waves using x-rays. To facilitate these experiments the PI is working with the Advanced Photon Source at Argonne National Laboratory (APS) and the National High Magnetic Field Laboratory in Tallahassee and Los Alamos to upgrade access to high magnetic fields at the APS. In organic and pnictide conductors anion or element substitution and moderate pressure make it easy to traverse the temperature-carrier concentration phase diagram that is ubiquitous among superconducting materials. Tuning the system from the density wave insulating state, through superconductivity, and into a metallic state will provide evidence of the quantum critical point thought to be responsible for superconductivity. Understanding the competition between ground states is a central question in quantum materials and the quantum critical point is central to this problem. The combination of measurements, model calculations, and an extensive library of crystal samples will further the goal of understanding the physics of quantum materials.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.