Novel Quantum Phases in Unconventional Insulators

我的研究计划旨在发现新的量子相。数十亿个电子相互作用，产生量子纠缠的物质相，具有与单电子不同的显著新性质。在“经典”调谐中，使用温度作为调谐工具，当环境发生变化时，物质的相可以相互转换。例如，冰融化成水，当温度升高时，水就会沸腾成蒸汽。在量子调谐中，温度以外的参数被用来在低温下在量子相之间转换系统。从更熟悉的相中出现的非传统物质相的例子包括一个惊人的例子，超导是一种奇怪的物质相，当施加高压或化学替代时，超导从磁性金属中出现，超导是一种传输电流的奇异相。在这里，我提议通过探索相关绝缘体附近鲜为人知的区域来寻找新的物质量子相，在这些区域中，组成电子之间的强烈相互作用阻止了电传输。理论模型和初步实验表明，该区域电子之间的强相互作用为发现新的奇异物质相提供了肥沃的土壤。在这个研究计划中，我们建议对两类不同类型的相关绝缘体进行实验研究，以产生新的量子相。首先，我们探索了铜氧化物材料家族，在母体磁绝缘体中引入移动载流子后，就会出现高温超导现象。我们将通过实验探索在最强超导电性附近出现的新中间相物质的理论预测，证明与更好地理解从金属磁中出现的超导电性的情况显著不同。其次，我们探索新发现的非传统绝缘体家族，它们同时显示出金属和绝缘行为。在这些材料中，尽管大部分材料表现出与几乎不能移动的电子相对应的电绝缘性质，但互补测量出人意料地揭示了循环电子轨道的特征，正如对块体金属所预期的那样。从物质的这一非传统绝缘相出发，我们的目标是发现在外加压力和强磁场的组合下，这些材料最终转变为更传统金属的过程中出现的各种新型中间相。这种新型物质量子相的发现及其最终控制对于基于强纠缠多体而不是单电子量子物理的下一代量子电子学至关重要。因此，这项研究将被证明是下一代量子技术发展的关键要素，这是EPSRC确定的一个重大挑战。在这项研究中，我建议在强磁场中高压和低温的极端条件下，从理论上研究相关绝缘材料的选择，并期望发现新的物质中间相的新范例，以及这些非传统物质之间的不寻常的转换模式。

My research programme aims to discover new quantum phases. Billions of electrons interact with each other to yield quantum entangled phases of matter with striking new properties distinct from those of single electrons. In 'classical' tuning, phases of matter can transform between each other when their environment is altered using temperature as a tuning tool. For example, ice melts to water, which boils to steam when the temperature is increased. In quantum tuning, parameters other than temperature are used to transform the system between quantum phases at low temperatures. Examples of unconventional phases of matter that emerge from more familiar phases include the striking case where superconductivity - an exotic phase of matter that transports electricity without any resistance to its flow - emerges from a magnetic metal, when high pressures or chemical substitution is applied.Here, I propose to search for new quantum phases of matter by exploring the little understood regime near correlated insulators, where strong interactions between constituent electrons prohibit electrical transport. Theoretical models and preliminary experiments suggest that strong interaction between electrons in this region offers fertile ground for the discovery of new exotic phases of matter.In this research programme, we propose to experimentally study two different classes of correlated insulators for the emergence of novel quantum phases. Firstly we explore the copper-oxide family of materials in which superconductivity at high temperatures emerges upon introducing mobile charge carriers in a parent magnetic insulator. We will experimentally explore theoretical predictions for new intermediate phases of matter that emerge in vicinity of strongest superconductivity, proving markedly different from the better-understood case of superconductivity that emerges from a metallic magnet.Secondly we explore the newly discovered family of unconventional insulators that simultaneously display dichotomous metallic and insulating behaviours. In these materials, despite the bulk of the material exhibiting electrically insulating properties that correspond to virtually immobile electrons, complementary measurements unexpectedly reveal signatures of circulating electron orbits as expected for a bulk metal. Beginning from this unconventional insulating phase of matter, we aim to uncover various novel intermediate phases that emerge enroute to these materials' ultimate transformation to more conventional metals under a combination of applied pressure and high magnetic field.The discovery of such novel quantum phases of matter, and their ultimate control is crucial for the next generation of quantum electronics based on strongly entangled many-body instead of single electron quantum physics. As such, this study will prove a key element in the development of next generation quantum technologies, a grand challenge identified by the EPSRC. I propose to study a theoretically motivated selection of correlated insulating materials under a combination of extreme conditions of high pressures in strong magnetic fields and low temperatures in this fellowship, and expect to discover new paradigms of novel intermediate phases of matter, and unusual modes of transformation between these unconventional phases of matter.