Month 13 Presentation Prize Winners Announcement

This year, we have a joint win for our Month 13 Presentation Prize: congratulations to second year PGRs Joe Pitfield and Will Borrows. The prize was a £50 voucher.

The Month 13 presentations are given each October, where the PGRs give a presentation on their work to date and feedback scores are given by their peers. Joe’s presentation was titled ‘The search for new materials’ and Will’s was titled ‘Simulating heat flow in thermoacoustic devices’. Please find their abstracts below.

The search for new materials

Joe Pitfield


It is commonly understood that there is no universal a priori approach to predicting the nature of boundary regions between materials, nor one to enable theoretical design of novel materials within such regions. We present a developing method (RAFFLE; pseudo Random Approach For Finding (Local) Energy minima) learning from existing structural prediction methods [2][1], for the pseudo-random generation of atomic structures. Materials are characterised by decomposition of both bond angle and length, with these characterisations applied retroactively to generate new structures with profiles indicative of the isolated characteristic (in these cases, Energy of formation). This method is able to predict the existence of a series of structures of known one, two and three element systems, along with other geometries known [3] to exist for chemically similar structures (for the Transition metal dichalcogenides, both H and T phase structures predicted) and multiple stable phases identical stoichiometry structures (hexagonal and tetragonal and for Carbon) along with scopes over varying stoichiometries (HCP and FCC aluminium).

[1] Chris J. Pickard and R. J. Needs. ‘High-Pressure Phases of Silane’. Phys. Rev. Lett.97 (4 July 2006), p. 045504.
[2] Yanchao Wang et al. ‘Crystal structure prediction via particle-swarm optimization’. Phys. Rev. B82 (9 Sept. 2010), p. 094116.
[3] Anubhav Jain et al. ‘The Materials Project: A materials genome approach to accelerating materials innovation’. APL Materials1.1 (2013), p. 011002.

Simulating heat flow in thermoacoustic devices

Will Borrows


The thermoacoustic effect is a process by which sound is produced by the Joule heating of a thin film (a ‘thermophone’) with an alternating current [1]. While this effect has been known for more than a century [2], recent advances in the fabrication of nano-scale films have rejuvenated the field of thermoacoustics [3,4]. Despite this, thermophones have struggled to present themselves as an alternative to more conventional piezoacoustic speakers due to their low output efficiency.
Here we present an examination into the propagation of heat within and around a thermophone through both finite-element and finite-difference simulation of a device. We do this in order to gain a greater understanding behind the thermal processes which hinder thermophone efficiency. Of particular note is the effect of the Maxwell-Cattaneo correction to Fourier’s heat law [5], which accounts for the non-instantaneous nature of heat flow. By measuring the effect of this correction on the thermal fluctuations at the boundary between the thermophone and its surrounding medium, we are able to determine a trend for this correction. Going forward, we intend to more accurately calculate the expected sound output of a thermoacoustic device, as well as quantify the effects of this correction on the thermoacoustic efficiency.
[1] Ding, H. Nanoscale, 2019, v.11, p.5839-5860
[2] Preece, W. H. Proceedings of the Royal Society of London, 1880
[3] Shinoda, H. et al. Nature, 1999, v.400, p.853-855
[4] Xiao, L. et al. Nano Letters, 2008, v.8, no.12, p.4539-4545
[5] Cattaneo, C. Comptes Rendus Hebdomadaires des Seances de l’Academie des Sciences, 1958, v.145, p.431-433

Month 25 Presentation Prize Winner Announcement

We are delighted to announce that third year PGR Benjamin Pearce has won the Month 25 Presentation Prize- a £50 Amazon voucher. The Month 25 presentations are given each October, where the PGRs give a presentation on their work to date and feedback scores are given by their peers. Ben’s presentation was titled ‘Mode Interference and Directional Acoustic Stop Bands in Solid-Fluid Superlattices’. Please find the abstract below.

‘Mode Interference and Directional Acoustic Stop Bands in Solid-Fluid Superlattices’

Whilst there is a large amount of work on one-dimensional phononic crystals (superlattices) consisting of alternating layers of solid materials, there is comparatively little investigation of the properties of the equivalent solid/fluid system. These systems are predicted to exhibit a directional transmission response not available to solid/solid systems. This response stems from an interference between the symmetric and anti-symmetric modes of a submerged plate. This effect can lead to pronounced, angularly dependent reductions in transmission, for even a single solid layer submerged in fluid [1,2]. Extending this system from a single plate to a multilayer structure offers an interesting avenue for phononic crystal design [3]. Existing work largely neglects to consider the interaction of this interference with the Bragg modes of a such a periodic structure. Here we present a numerical and theoretical consideration of the effects of this interaction and how the choice of crystal geometry offers routes for the creation of large bandwidth directional stop bands.

[1] M. Seiji, “Phononic Bandgaps Pecuiar to Solid-Fluid Superlattices,” Jpn. J. Appl. Phys, 2015.
[2] Z. Sai, X. Bai-qiang and C. Wenwu, “Controlling The Angle Range in Acoustics Low-Frequency
Forbidden Transmission In Solid-Fluid Superlattice,” J. Appl. Phys, 2018.
[3] S. Zhang, Z. Y, L. Wei, G. Hu, X. Bai-qiang and C. Wenwu, “Low Frequency Forbidden Bandgap
Engineering Via A Cascade of Multiple 1D Superlattices,” J. Appl. Phys, 2018.

Harry Penketh submits his thesis!

Congratulation to PGR Harry Penketh, who recently submitted his thesis titled ‘“Control of white light emission for illumination and imaging”.

Harry discusses his project in more detail, and offers his advice for students at the start of their PhD journey:

“I have submitted my thesis, although perhaps submitted to my thesis would be a more accurate statement.

To shed some light on my delightfully vague thesis title: this project was sponsored by Dyson and therefore large sections of the research conducted remain protected by a non-disclosure agreement. Working around NDAs aside, I appreciate the broader perspective and additional development opportunities this close industry collaboration has produced.

As is no doubt the case with any job (yes, I’m going to call it a job), doing a PhD comes with its own unique rewards and challenges. In a cohort-based PhD programme one hears a good deal of the latter, but less often in my experience do we reflect on the many great perks that come with the job. I feel privileged to have been able to work with my excellent supervisors Jacopo and Bill and to have had those days (usually in a lab with a new toy) where it didn’t feel like work at all.

My honest and possibly controversial advice for (some) new students: don’t work too hard. How many problems will you solve by spending an extra 6 hours staring desperately at a screen that would have just clicked into place with a refreshed set of eyes and a cup of tea? Look after yourself and don’t forget to find enjoyment in the PhD process.

I’m currently enjoying a break from conventional work and getting stuck into some long overdue property renovation. I hope to remain in Exeter in the medium-term at least.

Harry was involved with various outreach activities during his time with the CDT, including co-organising the mini conference Exeter-Bath Knowledge Transfer in October 2019 with fellow CDT PGRs Iago Rodriguez Diez and Ben Hogan, and students from the Centre for Photonics and Photonic Materials (CPPM) at University of Bath.

Harry has co-authored the following publications:


Harry has presented at the following conferences and workshops:

  • Harry Penketh, poster presentation (on the topic of emitters in wavelength scale reflectors) at Dyson CDT industry visit, Malmesbury, England, 1st November 2017
  • Harry Penketh, poster presentation (on the topic of emitters in wavelength scale reflectors) at Complex Nanophotonics Science Camp 2017, Windsor, England, 25th July 2017


New Publication: Calcium-stannous oxide solid solutions for solar devices

Ned Taylor

Congratulations to final year PGR Ned Taylor, who is lead author of ‘Calcium-stannous oxide solid solutions for solar devices’, published in Applied Physics Letters last week.

Ned gives a short summary of his work:

In this work, the potential of calcium-doped stannous oxide is explored for its potential as an active layer in an all-oxide solar cell design. The authors find an alloy formed of doping Sn:Ca with ratio 7:1 in SnO to exhibit favourable electronic and optical properties for a photovoltaic material. A potential design is proposed for an all-oxide solar cell based around the aforementioned solid solution being the active layer, where TiO2 and CaO are the adjacent transport layers. This study is performed using first principles density functional theory methods to explore the systems. This work was funded jointly be the CDT and Solaris Photonics, with the work being conducted by Ned Taylor and Steve Hepplestone.

Ned’s previous publications include ‘The Fundamental Mechanism Behind Colossal Permitivity in Oxides’, which he co-authored with fellow CDT PGRs Francis Davies, Shane Davies and Conor Price.

New Publication: Zahid Hussain translates “Seven Brief Lessons on Physics” into Urdu

Final year PGR Zahid Hussain in partnership with Fasi Malik, University of California has translated Carlo Rovelli’s “Seven Brief Lessons on Physics” into Urdu. Their translation has just been published by Mashal Books, Lahore. Below, Zahid discusses his motivations and the importance of the book:

I am pleased to announce that our translation of Carlo Rovelli’s book “Seven Brief Lessons on Physics” into Urdu (Pakistan’s national language) has been published by Mashal Books, Lahore. This work is a part of my outreach activities under CDT Metamaterials XM2 to promote science to inspire young students and also, the general public. The reason for translating this interesting book into Urdu is to introducing new scientific developments and concepts of physics in a simple and easy-to-understand language. Secondly, I find it very useful to promote such work to those curious readers who cannot access them in English. A short description of the book is given below:

The book provides a very brief overview of the most fascinating aspects of the great intellectual revolution that has occurred in physics in the twentieth century. In a very simple language, Carlo Rovelli explains to us that the image of the world our ancestors carried with them in prehistoric times, was challenged by the Greek philosophers. Later on, Galileo, Copernicus and Newton’s scientific contributions caused a paradigm shift in our perception of the reality. Afterwards, in the wake of the 20th century, the birth of Quantum mechanics and Albert Einstein’s theory of relativity provided us with a new understanding of the physical world we live in. Now, we know that either it’s a world of very small objects (at the atomic scale) or the world of bigger objects which we can see with our eyes, the reality is quantized. Everything, known in this material universe and even all the fundamental forces of nature interact with matter through the particles. The most fascinating aspect of this simple book is that it leaves the reader with this conclusion that science shows us how to better understand the world and also reveals to us that just how vast is the extent of what is still not known.

Zahid began his translation in 2018, with three chapters published online, so this is the culmination of years of dedication. Congratulations to Zahid for this great achievement.

Advisory Board Chair Prof Miles Padgett awarded OBE in Queen’s Birthday Honours 2020

Very many congratulations to the Centre for Metamaterial Research and Innovation’s Advisory Board Chair Prof Miles Padgett OBE!

Miles was appointed Officer of the Order of the British Empire (OBE) in the 2020 Birthday Honours for “services to scientific research and outreach”.


He holds the Kelvin Chair of Natural Philosophy in the School of Physics and Astronomy at the University of Glasgow and leads an Optics Research Group covering a wide spectrum from blue-sky research to applied commercial development, funded by a combination of government charity and industry.


Miles is a Fellow of the Institute of Physics (FINSTP), was elected a Fellow of the Royal Society of Edinburgh (FRSE) in 2001, a Fellow of the Optical Society in 2011, and a Fellow of the Society of Photographic Instrumentation Engineers (SPIE) in 2012, and a Fellow of the Royal Society (FRS) in 2014

Prof Sir Roy Sambles receives knighthood in Queen’s Birthday Honours

Congratulations to Prof Sir Roy Sambles, who has been awarded a knighthood in the Queen’s Birthday Honours for his services to scientific research and outreach.

Roy has worked in the University’s Department of Physics since 1972, becoming a senior lecturer there in 1985, a reader in 1988 and was made Professor of Experimental Physics in 1991. He led the EPSRC Doctoral Training Centre in Metamaterials from its inception in 2014 to 2017 and now sits on the CDT Management Board.

He is an elected Fellow of the Royal Society and has published over 520 scientific papers.

Roy has made significant contributions to our understanding of the melting process, spin waves in metals, resistivity of thin metal films, molecular rectification, liquid crystal optics, plasmonics and microwave and acoustic metamaterials. His early work concerned unravelling, using electron microscopy, the fundamentals of melting and evaporation of metal particles. He then went on to explore Conduction Electron Spin Resonance and provided definitive studies at low temperatures of spin waves in alkali metals. Later in his career, he also opened up research into natural photonics where his pioneering studies of the photonic structures in butterfly wings paved the way for new research in this area.

He was elected a fellow of the Royal Society in 2002 and received the IOP’s Thomas Young Medal in 2003 and its Faraday Medal in 2012. He also received the George Gray Medal of the British Liquid Crystal Society in 1998.

He was a Council member of the EPSRC from 2008 to 2014 and he served on the Defence Science Advisory Committee from 2005 to 2011, sitting on the Board of the Counter-terrorism centre from 2006 to 2013. In 2018 he was made an honorary fellow of the Institute of Physics, having been its president from 2013-2017. He is currently chair of the Royal Society Research Grants Board.



New Publication: ‘Surface functionalized N-C-TiO2/C nanocomposites derived from metal-organic framework in water vapour for enhanced photocatalytic H2 generation’

Congratulations to PGR Zahid Hussain, who is lead author of the paper  ‘Surface functionalized N-C-TiO2/C nanocomposites derived from metal-organic framework in water vapour for enhanced photocatalytic H2 generation’, published in the Journal of Energy Chemistry.

Zahid’s previous publications include ‘MOF Derived Porous ZnO/C Nanocomposites for Efficient Dye Photodegradation’
published in ACS Applied Energy Materials, and ‘Structural, optical, electronic and magnetic properties of multiphase ZnO/Zn(OH)2/ZnO2 nanocomposites and hexagonal prism shaped ZnO nanoparticles synthesized by pulse laser ablation in Heptanes’  published in Elsevier Materials Chemistry and Physics.


In this work, we have successfully demonstrated that nitrogen/carbon co-doped (anatase and rutile) TiO2 phase junction nanoparticles, homogeneously distributed in N and carboxyl group functionalized porous carbon matrix can be synthesized via simple one-step pyrolysis of titanium-based metal-organic framework (Ti-MOFs), NH2-MIL-125(Ti). Introducing water vapour at high temperature during the pyrolysis of NH2-MIL-125(Ti) results in the functionalization of the carbon matrix with carboxyl groups as well as the creation of additional localized oxygen-rich N like interstitial/intraband states above the valence band of polymorphic TiO2 nanoparticles that further narrowed the energy bandgap. The derived N-C-TiO2/C phase junction composites retain the disc-like tetragonal morphologies and textural properties inherited from the NH2-MIL-125(Ti) precursor. Without loading any noble metal co-catalyst such as Pt, Au, Pd, the sample N–C-TiO2/CArW exhibits very promising photocatalytic H2 generation from water splitting.

David Newman and Kostas Chatzimpaloglou present at the Institute of Physics Current Research in Magnetism 2020: High Frequency Spintronics

Last month, 2nd year PGRs David Newman  and Kostas Chatzimpaloglou both gave contributed talks for the Institute of Physics Current Research in Magnetism 2020: High Frequency Spintronics, which was held virtually.

David Newman

David’s presentation was on “Spin current propagation through an epitaxial antiferromagnetic NiO layer”. In this talk, he demonstrated the use of the inverse spin Hall effect (ISHE) and X-ray Ferromagnetic Resonance (XFMR) measurements to observe a DC and AC spin current respectively propagating through an antiferromagnetic layer in a multilayer sample. This is intended to inform future studies on spin current propagation which is a vital step in the development of spintronic devices.

David says of his talk:

I found it a great experience to present my work as part of a programme filled with the big names in the research field and make more contacts within the community.


Kostas’ talk was titled “Time resolved magneto-optical study of spin-orbit torques (SOTs) in ellipsoidal CoFeB/Pt

Kostas Chatzimpalouglou

elements” and focused on results gathered from the development of a magneto-optical Spin Transfer Torque Ferromagnetic Resonance (STT-FMR) technique to explore the magnetization dynamics that arise in these devices in response to DC current excitation.

By comparing with a macrospin model simulation with experimental data, this proves that when DC current is large enough, the DC SOT is observed to act on the magnetization. However, the strong DC Oersted field produces similar features in the resonance to the effect of SOT. Thus, it is required careful fitting to determine the value of SOT.

Training and other events: September 2020 to December 2020

Please find below a table of all upcoming XM² training and other events from September 2020 to December 2020. Please note due to the current lockdown situation, dates and location are subject to change. All Beyond a PhD and Colloquia will take place online.

Induction is scheduled to take place in week beginning 21st September and will take place online. Students will be sent the full schedule once it has been set.


21.09.20-25.09.20 Induction Week 1st years All day via Zoom
28.09.20 Induction: Meet Your Pastoral Tutor 1st years 09:00-10:00 via Zoom
29.09.20 CDT Group Meetings (Chair Handover) 2nd years 13:30-14:30 via Zoom
30.09.20 Introduction to COMSOL 1st years 09:00-12:00 via Zoom
30.09.20 Induction: Meet The Technical Team 1st years 14:00-15:00 via Zoom
01.10.20 Introduction to Statistics 1st years 16:30-17:30 via Microsoft Teams
02.10.20 Metamaterials Colloquium- Minerva Prize Colloquium: Louisa Brotherson, University of Liverpool, ‘Absolute acoustic sensor calibration for quantifying lab-generated earthquake sources’ All PGRs 12:30-13:30 via Zoom
06.10.20 Introduction to Outreach with Exeter Science Centre All 11:00-11:30 via Zoom
08.10.20;15.10.20;22.10.20;29.10.20 Statistics All 1st years via Microsoft Teams
23.10.20 Beyond a PhD: Dr. Laura Stoica, Piezoelectric Materials Research Manager at Thales All PGRs 12:30-13:30 via Zoom
05.11.20 and 12.11.20 Statistics 1st years 16:30-17:30 via Microsoft Teams
13.11.20 Metamaterials Colloquia: Prof. Mario G. Silveirinha (University of Lisbon), “Nonreciprocal and Topological Electromagnetics” All PGRs 12:30-13:30 via Zoom
19.11.20 CBC: Mandatory Session 1st years 09:30-11:00 or 11:30-1pm (sign up via Doodle poll) via Microsoft Teams
04.12.20 Metamaterials Colloquia: Prof. Isabelle Staude (University of Jena),(title TBC) All PGRs 12:30-13:30 via Zoom