Self-sustained phases and topology in interacting quantum system
Lead Research Organisation:
University of St Andrews
Department Name: Physics and Astronomy
Abstract
Magnetic resonance techniques such as NMR or ESR are most important tools for material analysis and imaging, used in academia, industry and health care alike. While the involved technology is state-of-the-art, the underlying theoretical understanding of the involved physics dates largely back to the 1950s and earlier. It is thus not surprising that the theoretical foundations are not well adjusted for the description of modern strongly correlated materials, emergent phenomena, and the dominance of quantum fluctuations at low temperatures. For instance, the relaxation process of a nuclear spin system is mainly driven by the coupling to the electron bath via the hyperfine interaction. In the standard description the relaxation process is based on a high temperature expansion. This naturally results in an exponential relaxation, characterised by the commonly used time scales T1 and T2. Yet strong quantum fluctuations can change this exponential at shorter time scales, for which the used high temperature expansion becomes invalid. In this project we will extend the theory and incorporate the spatio-temporal imprint of the quantum fluctuations of correlated many-body systems. We will address the impact on conventional macroscopic resonance techniques as well as on the recent developments of micro- or nano-NMR. Using our findings, we can provide a guide for experiments using magnetic resonance imaging or echo techniques to probe the strong correlation effects. As a particular application, we will focus on diagnostic techniques for modern topological materials and for systems used for quantum information processing.
Taught courses (160 credits over 2 years)
Teaching (96 hours over 2 years)
Outreach (48 hours over 2 years)
Skills training (105 hours over 4 years)
Key words: Magnetism, NMR, interacting quantum system
Taught courses (160 credits over 2 years)
Teaching (96 hours over 2 years)
Outreach (48 hours over 2 years)
Skills training (105 hours over 4 years)
Key words: Magnetism, NMR, interacting quantum system
Organisations
People |
ORCID iD |
| Bernd Braunecker (Primary Supervisor) | |
| Stephanie Matern (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509759/1 | 01/10/2016 | 30/09/2021 | |||
| 1798540 | Studentship | EP/N509759/1 | 01/09/2016 | 08/10/2020 | Stephanie Matern |
| Description | Our work addresses how a small quantum system evolves from the moment it is brought into contact with an environment. System-environment interactions have been the subject of numerous studies over many years, from quantum computing to MRI scanning. The environment, formed by surrounding matter or radiation, is usually treated as a bath draining the system's quantum information away. But recently there has been increasing interest in the joint quantum dynamics of system and environment at initial short times. In our paper we address this quantum dynamics head-on. We carefully dissect a standard framework for system-environment dynamics such that we pick up systematically the collective of system-environment interactions and obtain analytical expressions for all times. This approach is not limited to a specific environment, but as an illustration we describe how precisely a spin decays in a metal such as used for magnetic resonance. The shape of the quantum driven decay is a direct consequence of the nature of the environment, which opens up the possibility to use our analytic understanding as a tool to extract information about the environment, or even to manipulate it. As an example for the latter we propose a temperature independent, quantum fluctuation driven protocol to cool a metal through an ensemble of spins. This could complement the standard adiabatic demagnetisation refrigeration when the latter becomes impractical at low temperatures. |
| Exploitation Route | Our work provides at detailed insight in the microscopic dynamics of a model systems relevant for many condensed matter systems. Primarily, this is of interest for other researcher as the understanding of the model system can be used to gain a deeper insight how to, for example, stabilise a given state or enhance coherence by utilising the environment. In terms of a future application, our proposal for a temperature independent cooling protocol might lead to improved refrigeration of nano systems. Furthermore, our insight in the systems dynamics are valuable for quantum computation and spintronics applications and devices. |
| Sectors | Digital/Communication/Information Technologies (including Software),Other |
| URL | https://journals.aps.org/prb/abstract/10.1103/PhysRevB.100.134308 |
| Description | School Visit |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Schools |
| Results and Impact | This event in association with SHINE was aimed at a small group of pupils (12yr). I gave a talk about my research and discussed with the pupils afterwards how and if science and art go together. Based on my research, the pupils composed a piece of music with the help of the electric voice theatre which was performed at a concert 'Echoes fae Fife'. |
| Year(s) Of Engagement Activity | 2018 |
| Description | School Visit |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Schools |
| Results and Impact | Science day run by a regional school to promote girls in STEM subjects. We had a small workshop for what we use laser/light for, with a focus on communication infrastructure. The all day activity reached around 100 pupils (13-15 yrs). We got very good feedback from the school, such that we were asked to run the workshop again the year after. |
| Year(s) Of Engagement Activity | 2016,2017 |
| Description | Science Discovery Day |
| Form Of Engagement Activity | Participation in an open day or visit at my research institution |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Public/other audiences |
| Results and Impact | Open day of my research facility aimed at families, which runs every year. The aim is to show the general public the research at my university, the event is especially aimed at children to spark interest in science in general. Many parents reported that they have visited the open day before. |
| Year(s) Of Engagement Activity | 2019,2020 |