Quantum Optics of Giant Rydberg Excitons in Cuprous Oxide

Cuprous oxide (Cu2O) is one the oldest, and yet least well-known, semiconductor material. It has a slightly larger band gap than silicon, which means that the single crystal form of the material is slightly transparent in the visible part of the spectrum. Cuprous oxide exists in nature and beautiful deep-red gemstones have been cut and polished from natural single crystal material. There has been renewed recent interest in cuprous oxide as a technological material because of potential applications in photocatalysis and solar energy harvesting.

Cuprous oxide has an additional extraordinary optoelectronic property. In most semiconductors, photons with energy just larger than the band gap can produce bound electron-hole states known has excitons. These excitons are not unlike hydrogen atoms trapped in the solid-state: they consist of an electron orbiting a positive core (hole). Like hydrogen, the excitons also have excited states, which typically take the form of Rydberg series, and at cryogenic temperatures it is usually possible to observe a small number (3 or 4) excited states. Due to the unusual nature of the Fermi surface in cuprous oxide however, very high principal quantum number excitons states can exist. A recent Nature paper reported Rydberg series extending up to n = 25. This means that the exciton in cuprous oxide is an extraordinarily stable quantum object, and one that can be readily manipulated with light.

The aim of this PhD project is to investigate the quantum optical properties of this unique material and explore its potential to be exploited for quantum technologies. The student will join a well-funded medium-sized research group including two postdoctoral researchers and 5 PhD students. They will be trained in the use of a range of advanced spectroscopic characterisation tools, including ultrafast lasers and time-resolved transient FT-IR. They will also be trained in the latest cryogenic techniques, and additional materials characterisation tools including scanning-electron microscopy (SEM), confocal microscopy, and Raman spectroscopy. It is likely that the student will be required to spend some time abroad working with our international collaborators.

Start date: April, July or October 2021. 4 years Full Time.

How to Apply:

Applicants should submit an application for postgraduate study via the Cardiff University webpages (https://www.cardiff.ac.uk/study/postgraduate/research/programmes/programme/physics-and-astronomy) including:

• an upload of your CV
• a personal statement/covering letter
• two references
• Current academic transcripts

Applicants should select Doctor of Philosophy, with a start date of April, July or October 2021.

In the research proposal section of your application, please specify the project title and supervisors of this project and copy the project description in the text box provided. In the funding section, please select the ’self -funding’ option.

Candidates should hold a good bachelor’s degree (first or upper second-class honours degree) or a MSc degree in Physics or a related subject.

Applicants whose first language is not English will be required to demonstrate proficiency in the English language (IELTS 6.5 or equivalent).