Time-varying Acoustic Metamaterials Ref: 5050
About the award
Department of Physics, Streatham Campus, Exeter
The University of Exeter’s Centre for Metamaterials Research and Innovation (CMRI) with industry partners QinetiQ, is inviting applications for a fully-funded PhD studentship. For eligible students, the studentship will cover home tuition fees plus an annual tax-free stipend of at least £18,622 for 4 years full-time, or pro rata for part-time study. The student would be based in the Department of Physics and Astronomy within the Centre for Metamaterials Research and Innovation at the Streatham Campus in Exeter.
Metamaterial research is commonly concerned with designing sub-wavelength scale structures that exhibit effective material properties due to their engineered variation in space. A new paradigm for wave manipulation and information processing is booming due to the advent of time-varying metamaterials whose properties are modulated in time. New phenomena have emerged, beyond the limits set by energy conservation and time-reversal symmetry, enabling the control of wave momentum, frequency, and digital information, offering unique applications such as nonreciprocity, smart reconfigurable response, wave synthesis, and next-generation wireless communications, across electromagnetism, acoustics and mechanics [R. Sapienza, et al. APL 123.16 (2023)]. Time modulated media can even be used to mimic wave physics close to a black hole [J. B. Pendry, E. Galiffi, P. A. Huidobro, Photon conservation in trans-luminal metamaterials. Optica 9, 724–730 (2022)], with the associated emission of "Hawking radiation" [S. W. Hawking, Particle creation by black holes. Commun. Math. Phys. 43, 199–200 (1975)].
Significant time variation can be achieved using resonance: when two wave resonators are coupled, energy is exchanged and the wave eigenmodes are reshaped through strong coupling. If the coupling is dynamic and varies in time, on time-scales comparable to the coupling rates, the coupled system can be dramatically transformed: new resonant frequencies are formed, and the gain and loss of the coupled system is modified, both in total value (energy extraction from the coupling modulation) and in distribution between the two resonators [H. Ghaemi-Dizicheh arxiv:2302.00877 (2023)].
Classical, linear acoustics serves as a testbed for the exotic physics permitted by time-varying materials as the modulation timescales can be much faster than the coupling rates due to the (relatively) slow wave speed. This unexplored regime has the potential to allow for very fast modulation of the response of the coupled system and wave control, especially close to exceptional points [B. Longstaff et al. Phys. Rev. A 100, 052119 (2022); R. Melanathuru et al. Phys. Rev. A 10, 012208 (2022)]. In acoustics the overlap of the resonant fields can be modified via the spatial separation of the meta-atoms (e.g., Helmholtz resonators); this coupling shall temporally modulated using control electronics with e.g. single board Raspberry Pi computers.
This project will comprise a unique blend of theory, simulation and experimental verification; we will show theoretically that a temporally modulated coupling between two resonators can be transformed via a unitary gauge transformation to an effective system whose Hamiltonian is invariant under parity and time reversal. We will map the phase transition happening when the coupler modulation is comparable with the coupling rate, resulting in a non-reciprocal wave population transfer from one resonator to the other. We will verify experimentally that a non-parity time (PT) system, with non-balanced gain-loss medium can become PT-symmetric using time-modulated coupling between modulated acoustic waveguides dressed with sub-wavelength resonators.
About the Centre for Metamaterials Research & Innovation
You would be joining the doctoral training programme at the Centre for Metamaterial Research and Innovation (CMRI) at the University of Exeter. We support all our students in developing their scientific knowledge whilst also providing transferable and technical skills training to prepare them for careers within and outside of academia.
The PhD students learn together in targeted courses, self-driven activity groups, and exposure to industry to gain scientific background knowledge beyond their areas of expertise, and to equip themselves with transferable professional skills such as creative thinking, project management, and leadership. We are now home to a diverse community of over 30 active PhD students (Postgraduate Researchers, PGRs) who are training in a stimulating, challenging yet supportive cohort-based environment. Since 2018, over 65 graduates have entered employment in industry and as postdocs in Higher Education Institutions in and outside of the UK.
This award provides annual funding to cover Home tuition fees and a tax-free stipend. For students from the UK who pay Home tuition fees the award will cover the tuition fees in full, plus at least £18,622 per year tax-free stipend (increasing each year as per UKRI standard PhD stipend). The conditions for eligibility of home fees status are complex and you will need to seek advice if you have moved to or from the UK (or Republic of Ireland) within the past 3 years or have applied for settled status under the EU Settlement Scheme.
The studentship will be awarded on the basis of merit for 4 years of full-time study.
For further information on the project, please contact Dr Greg Chaplain via firstname.lastname@example.org, or telephone (01392 725654).
Applications are made to the Metamaterials programme for a PhD in Physics/Engineering. We invite candidates to specify their project(s) of interest at the time of application.
Please ensure to upload ALL items listed below through our application system. Incomplete applications cannot be processed.
Applicants for this studentship must have obtained, or be about to obtain, a First or Upper Second Class UK Honours degree, or the equivalent qualifications gained outside the UK, in Physics or an appropriate area of science or technology.
If English is not your first language you will need to have achieved at least 7.0 in IELTS and no less than 6.0 in any section by the start of the project. Alternative tests may be acceptable (see http://www.exeter.ac.uk/postgraduate/apply/english/).
How to apply
To apply for funding, you must do so by clicking on the ‘apply now’ button above. In the application process you will be asked to upload several documents.
Please note our preferred format is PDF, each file named with your surname and the name of the document, eg. “Smith – CV.pdf”, “Smith – Cover Letter.pdf”, “Smith – Transcript.pdf
- You will need to provide a COVER LETTER that indicates your preferred area of study and/or preferred project,
- You will also need to upload a PERSONAL STATEMENT. We recommend that you describe (a) why you would like to study for a PhD; b) why you would like to focus on the identified area/project, c) any relevant expertise and d) your future career ambitions. We would also encourage you to describe the qualities that you believe will make you a great researcher (in particular as part of a team). Note: these details are not given in the application process but shortlisting will include assessment against these criteria.
You will also need to upload
- Transcript(s) giving full details of subjects studied and grades/marks obtained (this should be an interim transcript if you are still studying).
- Two references from referees familiar with your academic work. If your referees prefer, they can email the reference direct to [Email Address Removed] quoting the studentship reference number. Please indicate this when you upload their details.
- If you are not a national of a majority English-speaking country you will need to submit evidence of your proficiency in English. Please see the entry requirements information above.
We intend to undertake interviews and make offers on a rolling basis following the deadline.
Note that we cannot accept references from personal/private email accounts, unless it is a scanned document on institutional headed paper and signed by the referee.
All application documents must be submitted in English. Certified translated copies of academic qualifications must also be provided (if applicable).
We foster creativity and utilisation of individual strengths. Applicants are encouraged to provide evidence to support their statements. This might include conventional written documents (e.g., examples of work), but we also encourage alternatives such as audio or video recordings, websites, programming etc. Please ensure to include accessible links to such files in an appropriately named document as part of the upload process
If you have any general enquiries about the application process or the project itself please email email@example.com
Applications will normally be reviewed within two weeks of receipt. Candidates will be short-listed against a set of agreed criteria to ensure quality while maintaining diversity. Failure to include all the elements listed above may result in rejection.
The essential criteria
• Undergraduate degree in a relevant discipline;
• Vision and motivation (for research & professional development);
• Evidence of the ability to work collaboratively and to engage in a diverse community;
• Evidence of excellent written and oral skills in English.
The highest quality candidates will also be able to demonstrate one of more of the following:
• Specialist knowledge about one or more of our research areas (see www.metamaterial.center);
• Training in research methodology (e.g., undergraduate research projects);
• Research outputs (e.g., papers) and/or other indicators of academic excellence (e.g. awards).
Shortlisted candidates will normnally be invited to an entry interview to assess fit to the cohort-based docotoral training programme, criteria above, and academic suitability.
Interviews are expected to start within two weeks upon application receipt. It is therefore advisable to apply as soon as possible.
|31st January 2024
|Number of awards:
|For eligible students the studentship will cover Home tuition fees plus an annual tax-free stipend of at least £18622 for 4 years full-time, or pro rata for part-time study.
|Duration of award:
|Contact: Metamaterials admissions tutor