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密不可分。从石器时代，青铜器时代，铁器时代，到所谓的硅时代，人类的时代是由他们那个时代的材料创新来区分的。20世纪最重要的发明是晶体管，这种由硅制成的器件奠定了当今所有信息技术的基础，是世界各地物理学家几十年来研究固体中电子行为的成果。我们的文明现在正处于量子时代的黎明，它将建立在展现量子世界全部丰富性的新材料的基础上。******今天渗透到量子材料领域的新思想是涌现，纠缠和拓扑。它们既有基础意义，也有技术意义。我提出的研究将探索这三个方面。******我的第一个目标是阐明赝隙相的性质，这是铜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难题之一。最近的想法表明，我们正在处理一种新的物质状态，具有拓扑秩序和一个新兴的希格斯场，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，我将用新的测量方法在高磁场中探测几种铜材料的赝隙相。这里的成功将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，这是一种引人注目的现象，通过这种现象，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。现在很清楚，这里涉及的高度纠缠的电子与宇宙中最高熵的物体——黑洞——有着密切的联系。我将探讨普朗克耗散在许多材料中的作用，在非常低的温度下使用不同的测量方法。在我的实验室里研究奇怪的金属所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，在一定条件下，某些磁性绝缘体在低温下形成磁有序的趋势受到阻碍，而低温态则是一种量子自旋液体，没有秩序。这种物质的新状态还没有得到实验的确切证实。然而，最近对一种材料的量子化热霍尔电导率的观察提供了量子自旋液体的诱人证据，这种液体具有被称为马约拉纳费米子的拓扑激发。我的第三个主要目标是证实这一革命性的观察，并探索这一光明的新领域。对马约拉纳费米子的明确观察可能会开启拓扑量子计算的时代，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.