Novel phases and phenomena in quantum materials

人类文明的进步与其制造和使用材料的能力交织在一起。从石器时代、青铜时代、铁器时代到可以被称为硅时代，人类时代的不同之处在于他们所处时代的材料创新。20世纪最重要的发明是晶体管，这是一种由硅制成的设备，是当今所有信息技术的基础，是世界各地物理学家数十年来了解电子在固体中的行为的工作的顶峰。我们的文明现在正处于量子时代的黎明，量子时代将以新材料为基础，充分体现量子世界的丰富性。 今天渗透到量子材料领域的新概念是浮现、纠缠和拓扑。它们既有根本的影响，也有技术的影响。我提议的这项研究探索了这三个方面。 我的第一个目标是阐明伪隙相的性质，这是铜酸盐超导体中存在的一种神秘的电子相，被广泛认为是物理学中的主要谜题之一。最近的想法表明，我们正在处理一种新的物质状态，具有拓扑秩序和浮现的希格斯场，这让人想起最近在欧洲核子研究中心发现的希格斯玻色子。为了探索这种可能性，我将在强磁场中用新的测量方法来探测几种铜酸盐材料的赝隙相。这方面的成功可能会使新的高温超导体的设计成为可能。 我的第二个目标是理解普朗克耗散，这是一种显著的现象，即某些金属中的电子流动受到普朗克常数设定的散射时间的限制。现在很明显，这里涉及的高度纠缠的电子与宇宙中最高熵的物体--黑洞--深度相连。我将通过在非常低的温度下进行各种测量，在一些材料中探索这种普朗克耗散。在我的实验室里通过研究奇怪的金属获得的知识可能会促进我们对量子引力和混沌的理解。 理论上已经确定，在某些条件下，某些磁性绝缘体在低温下形成磁有序的趋势是受阻的，而低温状态则是一个无序的量子自旋液体。这种新的物质状态还没有得到实验的确凿证实。然而，最近对一种材料中量子化的热霍尔传导性的观察提供了诱人的证据，证明了一种量子自旋液体，其拓扑激发被称为Majorana费米子。我的第三个主要目标是证实这一革命性的观察，探索这一光明的新前沿。对马约拉纳费米子的明确观测可能会开启一个拓扑量子计算时代，一些公司已经在探索这种可能性。

The progression of human civilization is intertwined with its ability to make and use materials. The ages of humanity are distinguished by the materials innovations of their time from the Stone Age, the Bronze Age, the Iron Age, to what can be called the Silicon Age. The most important invention of the 20th century is the transistor, a device built from silicon that underlies all information technology today the culmination of several decades of work by physicists worldwide to understand how electrons behave in solids. Our civilization is now at the dawn of the Quantum Age, which will be based on new materials that manifest the full richness of the quantum world. The new ideas that permeate the field of quantum materials today are emergence, entanglement and topology. They have both fundamental and technological implications. The research I propose explores all three. My first objective is to elucidate the nature of the pseudogap phase, a mysterious electronic phase present in cuprate superconductors, widely considered one of the major puzzles in physics. Recent ideas suggest we are dealing with a new state of matter, with topological order and an emergent Higgs field reminiscent of the Higgs boson recently discovered at CERN. To explore this possibility, I will probe the pseudogap phase of several cuprate materials with new measurements in high magnetic fields. Success here could enable the design of new high-temperature superconductors. My second objective is to understand Planckian dissipation, a remarkable phenomenon whereby the flow of electrons in some metals is limited by a scattering time set by Planck's constant. It is now clear that the highly entangled electrons involved here are deeply connected to the highest entropy objects in the cosmos: black holes. I will explore this Planckian dissipation in a number of materials, using various measurements at very low temperature. The knowledge gained by studying strange metals in my lab may advance our understanding of quantum gravity and chaos. It is well established theoretically that under certain conditions the tendency of certain magnetic insulators to form magnetic order at low temperature is frustrated, and the low-temperature state is instead a quantum spin liquid, without order. This new state of matter has not yet been solidly confirmed by experiment. However, the very recent observation of a quantized thermal Hall conductivity in one material provides tantalizing evidence of a quantum spin liquid, with topological excitations called Majorana fermions. My third major objective is to confirm this revolutionary observation and explore this bright new frontier. The definitive observation of Majorana fermions could usher in an era of topological quantum computing, a possibility that is already being explored by some corporations.