Novel Quantum Phases in Unconventional Insulators

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.