Strain-Tuning of Emergent states of Matter

Future technologies such as spintronics or integrated quantum sensors require materials that do not only have outstanding electronic properties but incorporate intricate complex magnetic and structural functionalities. One large class of compounds that has the potential to play a key role in such technologies are 'Quantum Materials'. The overarching commonality is that the properties of these materials are governed by quintessential quantum mechanical phenomena e.g. stabilising coherent many body phases which are driven by electron-electron interactions. The physics of these truly advanced materials is governed by a strong interplay between different competing magnetic, charge and orbital degrees of freedom with the emergent phenomena often posing a fundamental challenge to our current level of understanding.

A feature central to our proposal is that the large number of competing or cooperating charge and spin orders result in an extreme tunability of the physical properties of quantum materials - they are highly sensitive to external stimuli. This sensitivity of course makes them very attractive for applications which require controlling currents, magnetism or sensing environmental parameters. Here we will exploit this tunability through uniaxial strain, a key control parameter which has received increased attention recently. Its capability for selective symmetry control by lattice straining has been very successful in strongly changing superconducting transition temperatures, stabilising completely new phases, or changing the coupling between charge and spin density waves by symmetry control.

A study of the strain-stabilized electronic states in quantum materials is technologically very challenging, requiring ideally in-situ strain tuning and spectroscopic characterization of the electronic states. We recently succeeded in combining atomically resolved spectroscopic imaging of the electronic properties of materials by scanning tunnelling microscopy with in-situ tuning of uniaxial strain. This provides a step change in our capabilities to study the impact of strain on emergent orders and the electronic structure. Combination of the atomic-scale characterization with macroscopic measurements of the properties of the strain stabilized phases will provide new insights into the interplay between the microscopic physics found at the atomic scale and macroscopic properties of the material. It will also enable us to identify new ways to manipulate emergent phases of matter using uniaxial strain.

The proposed research programme is aimed at transformative advances in our understanding of competing interactions in quantum materials through the development of new experimental methods to characterise quantum materials under uniaxial strain. At the center of the proposed research are the possibilities of atomically resolved spectroscopic imaging of the evolution of electronic states under in-situ uniaxial strain tuning by low temperature scanning tunneling microscopy. This technologically step change will enable unique microscopic insights into strain-tuned electronic states and emergent phases. To this end, we will commission advanced custom built instrumentation which may well become of interest for research-oriented companies. We will explore existing connections to high tech companies to discuss possible commercialization of instrumentation developed over the course of this research programme.

Scientifically, the methods developed and new results emerging from this research programme will provide a new perspective on the physics of quantum materials. To maximize impact in the scientific community as well as widen the base of academic beneficiaries, we will organize a focused workshop surrounding the research proposed here. This workshop will serve to foster collaboration, identify future directions and discuss results from the research programme with the community as well as industrial partners we plan to invite.

The new methods developed and knowledge obtained will be of interest for (i) researchers working on the physics of quantum materials, for whom our results will provide new benchmark results to test existing as well as stimulate new theoretical approaches to the interdependence between the symmetry of emergent electronic phases and the underlying lattice structure, (ii) material scientists developing new quantum materials by providing new avenues for the tuning and investigation of their properties and (iii) other research groups working on quantum materials using complementary methods, with whom we will collaborate to gain a better understanding of the physics of quantum materials. Potentially interested parties in the UK are researchers working in quantum materials, spintronics, electronic structure and magnetic materials.

Establishing better control over and new ways to manipulate emergent phases of matter potentially leads to new ways to exploit the properties of quantum materials for applications. Our research programme underpins development of new materials-based quantum technologies, which in the long-term might have substantial economic implications.
Beyond academic impact, for highly developed countries like the UK with diminishing natural resources, the education of the workforce is the key economic factor to maintain competitiveness in an increasingly globalized economic environment. Through our dedicated PhD education programme at the Condensed Matter DTC in St Andrews and research fellows we will contribute to the training of professionals and experts with relevant specialized skills in quantum materials and designing and developing advanced instrumentation. This research and training will contribute to the job market in the UK through highly trained and educated individuals.

Part of our ongoing activities that will be supported by this research grant is an active outreach programme with local schools in which the investigators together with the PDRAs will take part. To engage with the general public we will highlight the research at science fairs, as well as by publicising our research through the websites of the investigators, social media, media interviews, press releases and news items aimed at the general public.