New Publication: Coupling and confinement of current in thermoacoustic phased arrays

Credit: David Tatnell

Congratulations to third year PGR David Tatnell, whose publication ‘Coupling and confinement of current in thermoacoustic phased arrays’ has just been published in Science Advances and featured on the University’s research news webpage.

David, lead author of this study into thermoacoustic arrays, says:

This work is the first experimental demonstration of thermoacoustic sources in acoustic phased arrays.

We find that thermoacoustic arrays are capable of reproducing all of the effects of traditional speaker arrays, such as beam forming and steering, but also have additional characteristics unique to this generation mechanism.

We show that we can exploit these characteristics to radically simplify array design, allowing for thermoacoustic phased arrays to be made smaller, and more economically, than traditional speakers. This includes creating a fully controlled array from nothing more than a thin metal film attached to some metal wires. Combined with the ability to make the speakers flexible and transparent, thermoacoustic arrays have many potential applications, such as haptic feedback systems in smartphones and other wearables.

This paper represents two and a half years of hard work, sponsored by QinetiQ and EPSRC.

Check out the University’s main research news webpage, which explores these findings and their significance in further detail.

 

New Publication: Coherent Transfer of Spin Angular Momentum by Evanescent Spin Waves within Antiferromagnetic NiO

David Newman

Congratulations to second year PGR David Newman, who has co-authored ‘Coherent Transfer of Spin Angular Momentum by Evanescent Spin Waves within Antiferromagnetic NiO’, recently published in Physical Review Letters. Out of the fourteen co-authors, David is listed fifth. His supervisors Dr. Maciej Dąbrowski and Prof. Robert Hicken are also co-authors.

The publication was also the subject of a Physics Viewpoint article, titled ‘Spin Current in an Antiferromagnet is Coherent’. It has also been featured on the University’s research news as an important breakthrough with the potential to lead to new high speed energy efficient data technology.

New Publication: ‘Microwave Superdirectivity with Dimers of Helical Elements’

Congratulations to third year PGR Pavel Petrov, whose article ‘Microwave Superdirectivity with Dimers of Helical Elements’ was published yesterday in Physical Review Applied.

Pavel summarises his article:

This paper demonstrates experimental realisation of the subwavelength superdirective antenna that reaches close to theoretical maximum of directivity without using complex feeding network. We introduce a novel design of superdirective dimer using helical elements, and describe how parameters of such structures can be optimised using our analytical method. We than show how the geometric parameters of helices and the conductivity of material used may affect directivity, efficiency and gain of the optimised dimer structure. This work is a result of the year and a half of hard work which has been sponsored by DSTL and is a part of SYMETA collaboration.

William Ferguson submits his thesis!

William Ferguson with his thesis

Congratulations to William Ferguson, the first of our 2016 cohort to submit their thesis. His thesis was titled ‘Auxetic power amplification mechanisms for low frequency vibration energy harvesting’. William was supervised by Prof. Meiling Zhu, Prof. Ken Evans and Prof. Christopher Smith.

William has published two papers- ‘Student Perspectives On The Concurrent Engineering Challenge 2017’ in Proceedings of the 2nd Symposium on Space Educational Activities; ‘Auxetic Structure for Increased Power Output of Strain Vibration Energy Harvester’ in Sensors & Actuators A. Physical.

During his time in the CDT William has been involved in outreach initiatives such as being a support volunteer for Soapbox Science and demonstrating magnetism to the public as part of Lighting Up Ramm.

In his own words, William describes his experience as a PhD student:

My thesis is done!
Years of swearing at machines, months of banging my head against a keyboard, weeks of procrastinating editing, days of fiddling with MATLAB until the graphs are presentable; all of it came down to collecting the bound theses less than an hour before the printshop closes for who knows how long. So that was fun.
I’ve learnt a lot in the last three and a half years. Such as how to effectively manage people. Perseverance. Systematic problem solving. And thyself. Peaking behind the academic curtain was all very fine and pleasant, but now I’d like to see how the rest of the world compares.
Incidentally, do look me up if you or someone you know is in need of a holistic engineer (a job title I’m trying to give traction, defined as: one who builds/designs with an appreciation of the interconnectedness of all things, often because they’ve been wrapped in gaffer tape by said engineer).

All the best,
William Ferguson

William presented at the following conferences:

  • Ferguson, W; Evans, K; Smith, C; Zhu, M, Poster: “Auxetic Design in Vibration Energy Harvesting”, Materials for Clean Energy Conference, London, United Kingdom, 8th April 2019.
  • Ferguson, W; Kaung, Y; Evans, K; Smith, C; Zhu, M, Poster: ‘Auxetic Enhancement of Vibration Energy Harvesting’, PSMA Inaugural International Energy Harvesting Workshop, Cork, Ireland, 28th May 2018
  • (William was a contributor to presentation and conference paper), Doerksen, K; Klooster, TGE; ‘Student Perspectives On The Concurrent Engineering Challenge 2017’, 2nd Symposium on Space Educational Activities, Budapest, Hungary, 10th April 2018
  • Ferguson, W; Kaung, Y; Evans, K; Smith, C; Zhu, M, Poster: ‘Auxetic Enhancement of Vibration Energy Harvesting’, Materials Research Exchange, London, England, 11th March 2018
  •  Ferguson W; ‘Power’, Concurrent Enginnering Challenge 2017,  Redu, Belgium, 11th September 2017
  •  Ferguson W; Li Q; Kuang Y; Zhu M; Poster: ‘Auxetic Strain Amplification For Enhanced Energy Harvesting Power’, Energy Harvesting Network 2017,  Manchester, England, 5th April 2017

 

New Publication: Dynamics of spiral spin waves in magnetic nanopatches: Influence of thickness and shape

Congratulations to fourth year PGR David Osuna Ruiz, whose paper ‘Dynamics of spiral spin waves in magnetic nanopatches: Influence of thickness and shape’ was published in Physical Review B last month. The co-authors include CDT alumnus Erick Burgos Parra. An abstract of the paper is below:

Abstract

We explore the dynamics of spiral spin waves in permalloy nanoelements with variable aspect ratio of geometric dimensions, and their potential use as improved spin wave emitters with no or little biasing field required. Numerical results show that above a certain thickness, propagating spiral waves can be obtained in circular and square shaped elements in a flux closure state. VNA-FMR experiments on 20-nm (thin) and 80-nm (thick) samples confirm two type of spectra corresponding to different dispersions for thinner and thicker elements. We show that, for the thicker films, the vortex core region acts as a source of large amplitude spiral spin waves, which dominate over other modes. In case of the thinner elements, these modes are critically damped. For different shapes of the patch, we show that a rich collection of confined propagating modes can also be excited, modifying the final wave front and enriching the potential of the nanodot as a spin wave emitter. We give an explanation for the intense spiral modes from the perspective of a balance of dipolar and exchange energies in the sample.

Liam Trimby passes his viva!

Congratulations to Liam Trimby, who has passed his viva. He was supervised by Prof. C. David Wright and Dr. Anna Baldycheva.Liam’s thesis was titled ‘Phase-Change Meta-Devices for Tuneable Bandpass Filtering in the Infrared’. The examiners were Prof. Martin Cryan from University of Bristol  and the internal examiner was Dr. Mustafa Aziz.

His achievements include winning the poster prize at CHAMP/WAFT conference in May 2018 for his poster on Multispectral Imaging using Phase-Change Meta-Filters.

Liam has also been heavily involved in outreach, having been a Metabuddies Lead Tutor (a schools outreach scheme run by CDT students) and a tutor for Brilliant Club KS4 (an outreach scheme targeted at disadvantaged Key Stage 4 students), as well as volunteering at WOMAD in 2017 and Pint of Science in 2019

Liam has co-authored the following publications:

2019

2018

2017

Liam has presented at the following conferences:

  • Liam Trimby, Anna Baldycheva, David Wright, Poster: “Chalcogenide Perfect Absorbers for the Detection and Modulation of Infra-Red Radiation” Defence Materials Forum, Exeter, United Kingdom, 17th April 2016.
  • Liam Trimby, David Wright, “Phase-Change Metadevices Incorporating GaLaS”, Knowledge Transfer Network – Indstrial Applications of Metamaterials, London, United Kingdom 29th March 2017.
  • Liam Trimby, Anna Baldycheva, David Wright, Poster: “Multispectral Imaging using Phase-Change Meta-Filters”, SPIE West, San Francisco, California, 27th January –  1st February 2018.
  • Liam Trimby, Anna Baldycheva, David Wright, Poster: “Multispectral Imaging using Phase-Change Meta-Filters”, 2nd International Symposium on Doped Amorphous Chalcogenides and Devices, Lake District, United Kingdom, May 2018
  • Liam Trimby, John Lincolin, Anna Baldycheva, David Wright, “Tunable Band-Pass Filters using Phase-Change Materials” 4th Cranfield Defence and Security Symposia, Swindon, United Kingdom, 13th – 14th November.
  • Liam Trimby, Anna Baldycheva, David Wright, Poster: “Tunable Band-Pass Filters using Phase-change Materials”, European Phase-Change and Ovonic Symposium, Catania, Italy, 8th – 10th September, 2018.
  • Liam Trimby, Anna Baldycheva, David Wright, Poster: “Tunable Band-Pass Filters using Phase-Change Materials”, Smart NanoMaterials, Advances, and Applications, Paris, France, 10th – 13th December 2018.
  • Liam Trimby, David Wright, Presentation: “Tunable Band-Pass Filters using Phase-change Materials”, MRS Spring 2019, Phoenix, Arizona, 22nd – 26th April 2019.
  • Liam Trimby, Yat-Yin Au, and C. David Wright, “Electrical switching behaviour of Ge2Sb2SexTe5-x thin films using in-suti micro-heaters”, EPCOS 2019, Grenoble France, 8th – 10th September 2019.

 

Carlota Ruiz De Galarreta passes her viva!

We are delighted to announce that Carlota Ruiz De Galarreta  has passed her viva. She was supervised by Prof. C. David Wright and Dr. Jacopo Bertolotti. Carlota’s thesis was on “Optical phase-change metasurfaces: novel design concepts to practicable devices”. The examiners were Prof Anatoly Zayats from Kings College London, and the internal was Dr Ana Neves from Exeter’s Department of Engineering.

In 2017, Carlota participated in Girls in STEM summer school, an event to encourage 11-13 year old girls to consider careers in STEM.

Carlota worked as a post-doc as part of Prof. C. David Wright’s research group from June this year and is currently a Visiting Research Fellow at Instituto de Óptica Daza de Valdés.

 

Carlota has co-authored the following publications:

2019

  • Ruiz De Galarreta Fanjul C, Alexeev A, Sinev I, Trofimov P, Bertolotti J, Wright CD. (2019) All-dielectric hybrid silicon/Ge2Sb2Te5 optical metasurfaces for tunable and switchable light control in the near infrared, Nanometa 2019: 7th International Topical Meeting on Nanophotonics and Metamaterials, Seefeld, Austria, 3rd – 6th Jan 2019. [PDF]
  • Cai L, Ruiz De Galarreta Fanjul C, Wright CD, Herapath R, Qiu M, Li Q, Hendry E. (2019) Terahertz Amplitude Modulators using Phase-Change Matematerials, ICMAT 2019 – 10th International Conference of Materials for Advanced Technologies, 23rd – 28th Sep 2019.
  • Ruiz De Galarreta Fanjul C, Wright CD. (2019) Non-Volatile, Reconfigurable, Multilevel Photonic Devices Based on Phase-Change Metasurfaces and Thin Films, 2019 MRS Spring Meeting, Phoenix, Arizona, Usa, 22nd – 26th Apr 2019.
  • Gemo E, Carrillo SGC, Degalarreta CR, Baldycheva A, Hayat H, Youngblood N, Bhaskaran H, Pernice WHP, Wright CD. (2019) Plasmonically-enhanced all-optical integrated phase-change memory, Optics Express, volume 27, pages 24724-24738, article no. 17, DOI:10.1364/OE.27.024724. [PDF]

2018

2017

  • Au Y-Y, Garcia-Cuevas Carrillo S, Ruiz De Galarreta Fanjul C, Wright CD. (2017) Infrared Phase-Change Meta-Devices with In-Situ Switching, E/PCOS 2017, Aachen, 3rd – 5th Sep 2017. [PDF]
  • Ruiz de Galarreta C, Alexeev AM, Bertolotti J, Cryan MJ, Klemm M, Wright CD. (2017) The design of practicable beam steering and beam shaping phase-change metasurfaces working at telecom frequencies, European Phase Change and Ovonic Symposium, EPCOS 2017, Aachen, Germany, 3rd – 5th Sep 2017, https://www.epcos.org/.
  • Alexeev AM, Ruiz De Galarreta C, Garcia-Cuevas Carrillo S, Sinev IS, Samusev AK, Gemo E, Nagareddy VK, Au Y-Y, Wright CD. (2017) Tunable Dielectric Metadevices Enabled by Phase-Change Materials, European Phase Change and Ovonic Symposium, EPCOS 2017, Aachen, Germany, 3rd – 5th Sep 2017, https://www.epcos.org/.

 

Carlota presented at the following conferences and workshops:

2018

  •  May 2018, IEEE symposium on circuits and systems (ISCAS 2018), Florence (Italy)- Presentation: ‘Phase-Change Metasurfaces for Dyamic Beam Steering and Beam Shaping in the Infrared’ (authors: C Ruiz de Galarreta, A. Alexeev, J Bertolotti,C D Wright)

2017

  • November 2017, 2017 MRS fall meeting, Boston (EEUU), Presentation: ‘Phase-Change Plasmonic Metasurfaces for Dynamic and Reconfigurable Beam Steering and Beam Shaping in the Near Infrared ‘, (authors: C Ruiz de Galarreta et al.)
  • October 2017, WAFT Scientific meeting 2017, Oxford (UK), Poster: ‘A Phase-change metamaterial-based dynamic beam steering device’ (authors: C Ruiz de Galarreta, A. Alexeev, J Bertolotti, M Cryan, M Klemm, C D Wright)
  • September 2017, E\PCOS conference 2017, Aachen (Germany), Poster: ‘The design of practicable beam steering and beam shaping phase-change metasurfaces working at telecom frequencies’ (authors: C. Ruiz de Galarreta,  A. Alexeev, J. Bertolotti, M.J. Cryan, M. Klemm, C.D. Wright)
  • April 2017, 2017 MRS Spring meeting, Arizona (EEUU), Presentation: ‘Tunable dielectric metadevices enabled by phase-change materials’ (authors: A Alexeev, C Ruiz de Galarreta, S Garcia-Cuevas Carrillo, I S Sinev, CD Wright, E Gemo, V K Nagareddy, DA Zuev)

2016

  •  October 2016, WAFT Scientific meeting 2016, Oxford (UK), Poster: ‘A Phase-change metamaterial-based dynamic beam steering device’ (authors: C Ruiz de Galarreta, J Bertolotti, M Cryan, M Klemm, C D Wright)
  • September 2016, E\PCOS conference 2016, Cambridge (UK), Presentation: ‘Phase-Change meta photonics’ (authors:  C David Wright, Carlota Ruiz de Galarreta, Liam Trimby, Santiago Garcia-Cuevas, Jacopo Bertolotti, Maciek Klemm, Martin Cryan)

Fun-COMP creates first ever integrated nanoscale device programmable with either photons or electrons

Congratulations to Prof. C. David Wright whose work as lead of the EU H2020 project Fun-COMP was featured on the University’s main news webpage.

The team have created the first-ever integrated nanoscale device programmable with either photons or electrons. This device helps achieve faster and more energy efficient computer memories and processors. Fun-COMP is a collaboration between researchers at Universities of Exeter, Oxford and Münster, along with IBM Zurich, Thales Saclay, IMEC and C2N-CNRS.

The findings are detailed in the paper Plasmonic nanogap enhanced phase change devices with dual electrical-optical functionality, which Prof. C. David Wright co-authored.

New Publication: ‘The Fundamental Mechanism Behind Colossal Permitivity in Oxides’

Congratulations to fourth year PGRs Francis Davies and Ned Taylor, third year PGR Shane Davies and second year PGR Conor Price, who have co-authored a paper with Dr. Steven Hepplestone. The paper, titled ‘The Fundamental Mechanism Behind Colossal Permittivity in Oxides‘, determines the mechanism responsible for colossal permittivity exhibited by various oxides to be that of a thin metallic region forming between two insulating oxides. The authors also present a method for engineering metamaterials with this unusual property.

This is an excellent example of cross-cohort collaboration within the CDT.

An abstract of the paper is below:

Abstract

Colossal permittivity materials exhibit extreme polarization in an applied electric field, providing applications in electronics and energy transmission. Understanding the atomic‐scale mechanism behind colossal permittivity remains a challenging task and is key to optimizing materials with this property. The fundamental mechanism of colossal permittivity is reported and, using CaCu3Ti4O12 as an example, it is attributed to the formation of an unusual metallic interface between the grain and grain boundary materials (CaCu3Ti4O12 and CuxO (x = 1, 2), respectively), not created by oxygen vacancies as is normally the case in oxide materials. This metallic layer around the grain forms confined shells of charge that pool on one side when under an applied field, which results in colossal permittivity. A route towards enhancing colossal permittivity is explained by means of manipulating the interface properties, as well as altering sample geometries. A methodology to artificially engineer colossal permittivity metamaterials is also shown.

Natalie Whitehead submits her thesis!

Congratulations to PGR Natalie Whitehead, who has just submitted her thesis on ‘Making The Grade: Generating and Controlling Spin Waves with a Graded Refractive Index’. Her supervisors were Prof. Volodymyr Kruglyak, Dr. Thomas Philbin and Dr. Simon Horsley.

During her degree, Natalie has been prolific in her Outreach work. As well as being part of Metabuddies, the CDT’s schools outreach scheme, she has had led and taken part in many outreach events and workshops, a particular favourite being a yearly Inspiring Science Lecture at Exeter College

Last year, Natalie spent a month with University of Manitoba, Canada, working with Prof. Bob Stamps on understanding the principles of ‘Coherent Perfect Absorption’ theoretically for both a mirror and a 2-way input, trying to implement for spin waves. Natalie said this was one of the highlights of her degree and that she learned a lot, as well as enjoying her visit to Canada.
She won Best Poster Award for poster “Theory of Spin Wave Emission from a Bloch Domain Wall” at JEMS 2016, and again in Magnonics 2018. Other achievements include nominations for the University of Exeter’s 41 Women Campaign 2015.

Natalie’s publications include:

Natalie presented at the following conferences:

  • January 2019- Intermag / MMM Conference 2019, Washington DC, USA (presentation on ‘Graded Index Lenses for Spin Waves), authors N.J. Whitehead, T.G. Philbin, S.A.R. Horsley, V.V. Kruglyak
  • July 2018-  ICMFS 2018, Santa Cruz, USA (poster on ‘A Luneburg Lens for Spin Waves, and  Theory of Linear Spin Wave Emission from a Bloch Domain Wall’), authors N.J. Whitehead, T.G. Philbin, S.A.R. Horsley, V.V. Kruglyak (+ A. N. Kuchko for latter)
  • July 2018-  ICM 2018, San Fransisco, USA (poster on ‘A Luneburg Lens for Spin Waves, and  Theory of Linear Spin Wave Emission from a Bloch Domain Wall’), authors N.J. Whitehead, T.G. Philbin, S.A.R. Horsley, V.V. Kruglyak (+ A. N. Kuchko for latter)
  • June 2018- SolSkyMag 2018, San Sebastian, Spain (poster on ‘A Luneburg Lens for Spin Waves’), authors  N.J. Whitehead, T.G. Philbin, S.A.R. Horsley, V.V. Kruglyak
  • June 2018- International Advanced School on Magnonics 2018, Kiev, Ukraine (poster on ‘Graded Index Lenses for Spin Waves’), authors N.J. Whitehead, T.G. Philbin, S.A.R. Horsley, V.V. Kruglyak
  • June 2018- ICMM 2018,  Exeter, UK (30 minute talk on ‘Graded Index Lenses for Spin Waves’), authors N.J. Whitehead, T.G. Philbin, S.A.R. Horsley, V.V. Kruglyak
  •  April 2018- Magnetism 2018, Manchester, UK (poster on ‘ Theory of Linear Spin Wave Emission from a Bloch Domain Wall’- awarded ‘best poster’ at conference), authors N.J. Whitehead, T.G. Philbin, S.A.R. Horsley, A.N. Kuchko, V.V. Kruglyak
  •  August 2017- Magnonics 2017, Oxford, UK (poster on ‘Theory of Linear Spin Wave Emission from a Bloch Domain Wall’), authors N.J. Whitehead, T.G. Philbin, S.A.R. Horsley, A.N. Kuchko, V.V. Kruglyak
  •  July 2017-  MagIC 2017, Poznan, Poland (presentation on ‘Theory of Linear Spin Wave Emission from a Bloch Domain Wall’), authors N.J. Whitehead, T.G. Philbin, S.A.R. Horsley, A.N. Kuchko, V.V. Kruglyak
  •  August 2016- JEMS 2016, Glasgow, UK, (poster on ‘Theory of Spin Wave Emission from a Bloch Domain Wall’, one of the ten ‘Best Posters’ out of over 500 submitted), authors N.J. Whitehead, T.G. Philbin, S.A.R. Horsley, A.N. Kuchko, V.V. Kruglyak
  •  June 2016- International Advanced School on Magnonics, Exeter, UK (poster on ‘Theory of Spin Wave Emission from a Rectangular Anisotropy Defect’, also host and co-organiser of conference), authors N.J. Whitehead, T.G. Philbin, S.A.R. Horsley, A.N. Kuchko, V.V. Kruglyak
  •  April 2016-  Magnetism 2016, Sheffield, UK (poster on ‘Theory of Spin Wave Emission from a Rectangular Anisotropy Defect’), authors N.J. Whitehead, T.G. Philbin, S.A.R. Horsley, A.N. Kuchko, V.V. Kruglyak

Next, Natalie is working on the ambitious task of opening a STEM + Art (“STEAM”) Science Centre in Exeter. She says:

“At the Exeter Science Centre, we aim to connect the science research institutions of the South West with the general public, providing an inspiring space for all. This space will be filled with engaging, hands-on exhibits which explain the awesome science that’s going on in the region, particularly around the themes of ‘Global Challenges’. Science will be interweaved with art throughout, to express and mirror the underlying creative process involved in every scientific endeavour.

 

Our goal is to educate and inspire the general public about science through our guided exhibits, regular public talks, events, and collaborations with CoachBright and other educational organisations. We want to give the public the tools, the inspiration and the motivation to make a difference in the world. “

More information on this exciting project can be found at exetersciencecentre.org.