Novel Quantum Phases in Unconventional Insulators

我的研究计划旨在发现新的量子相。数十亿电子相互作用，产生物质的量子纠缠相，这些相具有与单个电子截然不同的新特性。在“经典”调谐中，当物质的环境被温度作为调谐工具改变时，物质的相位可以在彼此之间转换。例如，冰融化成水，当温度升高时，水沸腾成蒸汽。在量子调谐中，使用温度以外的参数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常规物质相的例子包括一个引人注目的例子，当高压或化学替代应用于磁性金属时，超导现象——一种物质的奇异相，可以在没有任何阻力的情况下传输电流。在这里，我建议通过探索相关绝缘体附近鲜为人知的政权来寻找新的物质量子相，在那里组成电子之间的强相互作用禁止电传输。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。在本研究计划中，我们建议实验研究两种不同类型的相关绝缘体对新量子相出现的影响。首先，我们探索了氧化铜材料家族，其中在母磁性绝缘体中引入移动电荷载流子后，在高温下出现超导性。我们将通过实验探索在最强超导性附近出现的新的物质中间相的理论预测，证明与更好理解的金属磁铁出现的超导性的情况明显不同。其次，我们探索了新发现的非传统绝缘体家族，同时显示金属和绝缘的双重行为。在这些材料中，尽管大部分材料表现出与几乎不移动的电子相对应的电绝缘特性，但互补测量出人意料地揭示了循环电子轨道的特征，正如预期的大块金属。从这种非常规的绝缘阶段开始，我们的目标是揭示各种新的中间阶段，这些阶段出现在这些材料在施加压力和高磁场的组合下最终转变为更传统的金属的过程中。这种物质的新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因素，这是EPSRC确定的一项重大挑战。我建议在强磁场和低温的极端条件下，在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式，以及这些非常规物质相之间的不寻常转换模式。

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.