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HomeWelcome to my webpage. I am a theoretical physicist interested in the physical properties of new class of materials, two-dimensional crystals, as well as their stacks, often referred to as van der Waals heterostructures. Most of my work concerns graphene, the best known two-dimensional crystal first obtained by mechanical exfoliation of graphite and made of a single layer of carbon atoms arranged in regular hexagons, and its heterostructures (for example, graphene on hexagonal boron nitride or twisted bilayer graphene). I am also interested in layered transition metal dichalcogenides, especially those with Jahn-Teller/Peierls instabilities. As a side interest, I explore the benefits of applying the physicist's mindset to economics (vide econophysics). Information for potential PhD studentsIf you are interested in my research and would like to join me as a PhD student, please get in touch with me to discuss potential projects and available funding. Bear in mind that the possibility of a scholarship is much higher if you are a British/EU citizen. Also, early contact is crucial as some funding sources require applications submitted as early as December (for start in October the following year). News26/05/2023 - Learning about electronic states in graphene stacks with a twistOur work in collaboration with researchers from the University of Warwick and the University of Manchester (including a former student of mine, Aitor, who moved on to a postdoc in Manchester after his PhD in Bath) has been published in Nano Letters! We use angle-resolved photoemission spectroscopy to study the twist-dependent band structure of graphene stacks of various thicknesses, from two to four atomic layers. We show that our theoretical model describes all samples, irrespectively of the twist angle, thickness or the applied external out-of-plane electric field, very well. For the four-layer crystal (so called twisted double layer graphene) with a twist of 1.5°, we observe a flat band near the Fermi level with a bandwidth of about 30 meV. Full version of the article can be accessed here (the article is open access; preprint version available here). 28/04/2023 - From model building to forecastingOur work lead by Matthew has been finally published in the International Journal of Forecasting! He has used the model he developed earlier to forecast two important economic indicators of risk, value at risk and expected shortfall. He has shown that his novel Hawkes-type model performs better in predicting the most extreme gains and losses than the established industry models. Full version of the article can be accessed here (the article is open access; preprint version available here). 19/01/2023 - Congratulations to Will!Today, Will has successfully defended his thesis studying the charge density waves in 2H-TaSe2. Will has done an excellent job, with his paper under review at Physical Review Research and one more in the pipeline if he finds the time while working as a patent lawyer in London. 01/10/2022 - Welcome to Luke SonejiWelcome to Luke Soneji who is starting his PhD in my group. He is supported by EPSRC and will be studying the survival and impact of moiré effects in bulk layered crystals. 24/01/2022 - Topology of near-30-degree twisted bilayer grapheneOur work in collaboration with experimentalists from the University of Manchester and the Elettra Synchrotrone has been published in ACS Nano! Full version of the article can be accessed here (the article is open access; preprint version available here). 10/08/2021 - Earthquakes and financial marketsOur work connecting physics and financial markets has been published in Physical Review E - congratulations to Matthew who bravely ventured into the unknown lands of econophysics! In this paper, he has applied a model developed to describe the fore- and aftershocks in earthquake sequences to the extreme price changes of the S&P 500 stock market index. In both of these cases, the extreme events tend to follow each other closely, arriving in clusters. However, where the earthquakes are characterised only by their magnitude, financial returns can be both positive (gains) or negative (losses) - up to now, the question of how these two types of extreme event interact has largely been neglected. We have constructed a model describing separately the positive and negative extremes as well as the interaction between them and found that extreme losses excite the market more than twice as much as do extreme gains, and they do so with more than five times the immediacy. This result reflects an underlying negativity bias among market traders, while also providing a new tool to probe and predict extreme fluctuations within both financial markets as well as other drift-diffusion-like processes. 15/07/2021 - Choosing a direction in FlatlandOur work (in collaboration with the experimental group of Dan Wolverson here in Bath as well as photoemission experts at Soleil and ICMM Madrid) showing coupling between crystal thickness and in-plane anisotropy in mono- and few-layer ReSe2 has been published in Physical Review B. Congratulations to Surani who contributed her theoretical calculations to this work! 11/05/2021 - Congratulations to Surani!Today, Surani has successfuly defended her thesis discussing the electronic structure of rhenium dichalcogenides. During her PhD, Surani published two papers (one in ACS Nano and one in Journal of Electronic Materials). One more paper is currently under review in Physical Review B and one is being prepared for submission (yes, this certainly is a trend). 06/11/2020 - Raman spectroscopy for in situ optical control of angles in twistronic grapheneOur work in collaboration with researchers from the University of Manchester has been published in Physical Review Letters! Congratulations to Aitor and Joshua, who started this project while still PhD students in my group, for such a high-impact publication! Graphenes are layers of carbon atoms extracted from graphite and they commonly display semimetallic properties. When placed on top of each other with a small twist, they qualitatively change their electronic properties due to the formation of a periodic moiré pattern which strongly depends on the misalignment angle. We show that Raman spectra of electronic excitations in twistronic graphenes display features which reflect peculiar band structure properties of these stacks such as flat band dispersion intervals. Our proposal paves the way for in situ control of the twist angle in twistronic graphene devices over a broad range of angles. Full version of the article can be accessed here (article is open access; preprint version available here). 17/07/2020 - Determining interatomic coupling at van der Waals interfacesOur work in collaboration with researchers from the Oxford University, Peking University and Elettra Synchrotron in Italy has been published in Nature Communications! Congratulations to Joshua, who started this project while still a PhD student in my group, for such a high-impact publication! Full version of the article can be accessed here (article is open access; preprint version available here). It was also selected as a highlight of research performed using ELETTRA Synchrotron resources and made University of Bath news. 28/05/2020 - Visualizing Orbital Content of Electronic Bands in ReSe2Our work in collaboration with researchers from South Korea including the University of Seoul, Yonsei University, Sogang University and Sejong University as well as the Lawrence Berkeley National Laboratory in the US has been published in ACS Nano! Congratulations to Surani for such a high-impact publication! Full version of the article can be accessed here (subscription required; preprint version available here). 06/12/2019 - Congratulations to Aitor!Today, Aitor has successfuly defended his thesis discussing Raman spectroscopy of electronic excitations in graphene materials. During his PhD, Aitor published two papers (one in Physical Review B and one in Nano Letters) and is writing up a third one (this does seem to be a trend). He will be now moving on to a postdoctoral position at the National Graphene Institute at the University of Manchester. 01/10/2019 - Welcome to Matthew TomlinsonWelcome to Matthew Tomlinson who is starting his PhD in my group. Matthew, supported by CheckRisk LLP and EPSRC through a CASE scholarship, will be studying phase transitions in financial markets using the approaches from the physics of complex systems. 30/07/2019 - Electronic Raman scattering features of rhombohedral graphiteOur work in collaboration with researchers from the National Graphene Institute at the University of Manchester in the UK has been published in Nano Letters! Congratulations to Aitor for such a high-impact publication! Full version of the article can be accessed here (the article is open access; preprint version available here). 01/07/2019 - Senior LectureshipFrom the beginning of July, I have been promoted to the post of Senior Lecturer (Associate Professor)! 07/06/2019 - Congratulations to Joshua!Today, Joshua Thompson has successfully defended his PhD thesis on the electronic properties and electron transport in van der Waals heterostructures containing graphene. During his PhD, Joshua published two papers (one in Physical Review B and one in Physical Review Applied, both with valuable input from Damien) and is writing up a third one. He will be moving to a postdoctoral position at the Chalmers University of Technology in Sweden. 01/05/2019 - Welcome to Will LuckinWelcome to Will Luckin who is starting his PhD in my group. Will, supported by the Bristol/Bath Centre for Doctoral Training in Condensed Matter Physics, will investigate twisted homo- and heterostructures of transition metal dichalcogenides. 01/12/2018 - Excellence AwardI have been awarded the University of Bath Excellence Award for 2017/18! 30/08/2018 - Congratulations to Damien!After four years of hard work, Damien completed his PhD on the electronic properties of bilayer graphene-based van der Waals heterostructures! During his PhD, Damien published two papers (one in Physical Review B and one in Physical Review Applied with Joshua) and is writing up a third one. He will be moving on to a postdoctoral position at the Centre for Fine Print Research at the University of the West of England. 05/01/2018 - Interfacial polarons in graphene/hBNOur work in collaboration with researchers from SOLEIL Synchrotron in France, Institute of Physics of the Chinese Academy of Sciences in Beijing, Stanford University and Harvard University has been published in Nano Letters! Full version of the article can be accessed here (subscription required; preprint version available here). 30/06/2017 - I won the Maxwell Medal!In recognition of my work on the electronic properties of graphene, I have been awarded the James Clerk Maxwell Medal and Prize by the Institute of Physics. It feels very rewarding but is also a big motivation for me to continue my research. It also is a little intimidating, as the list of past recipients of this medal contains some very recognizable names in theoretical physics, including some Nobel Prize winners. You can read more about the award here. 01/05/2017 - Welcome to Surani GunasekeraSurani, funded partly by the University of Bath, started her PhD in my group after finishing her first year of lectures and projects within the Bristol/Bath CDT in Condensed Matter Physics. Her research will focus on the electronic properties of rhenium dichalcogenides. 01/05/2016 - Welcome to Aitor Garcia Ruiz-FuentesAitor started his PhD in my group after finishing his first year of lectures and projects within the Bristol/Bath CDT in Condensed Matter Physics. He will study the electronic properties of graphene with proximity-induced superconductivity. 01/04/2016 - Centre for Nanoscience and NanotechnologyA new research centre focused on nanoscience and nanotechnology has been established at the University of Bath. I have joined it as one of the founding Principal Investigators. 01/10/2015 - Welcome to Joshua ThompsonWith the beginning of the 2015/16 academic year, Joshua Thompson starts his EPSRC-funded PhD with me. Joshua will investigate the electronic properties of the graphene/hexagonal boron nitride heterostructures. 20/12/2014 - New chapter in BathIt's official! After finishing my two years as the University of Bath Prize Fellow in February 2015, I will continue my work at the University of Bath as a Lecturer (Assistant Professor). 01/12/2014 - Excellence AwardI have been awarded the University of Bath Excellence Award for 2013/14! 01/10/2014 - Welcome to Damien LeechWith the beginning of a new academic year, Damien Leech joins me as my first PhD student. His research into the electronic properties of two-dimensional crystals is funded by EPSRC. 12/09/2014 - Fermi surface of bilayer graphene breaks into piecesOur work in collaboration with researchers from ETH Zurich, NIMS Tsukuba and Lancaster University has been published as a cover article in Physical Review Letters!
Bilayer graphene turns out to be a very special case because its electronic spectrum can be tuned by applying an external electric field. By studying bilayer graphene in strong electric fields, we identified signatures of its Fermi surface changing from a singly-connected one into one composed of three separate pieces. Interestingly, our team observed that in external magnetic field the electron topological transition leads to other, interaction-driven transitions between electron states as the change in topology affects the repulsion between electrons. Full version of the article can be accessed here (subscription required; preprint version available here). |
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