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Welcome 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 students

Below, you can find links to short descriptions of examples of PhD projects available in my group. If you are interested in my research and would like to join me as a PhD student, please get in touch with me to discuss 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).

Again, feel free to email me if you want to discuss these or other research ideas or the availability of funding.


News


30/07/2019 - Electronic Raman scattering features of rhombohedral graphite

Our work in collaboration with researchers from the National Graphene Institute at the University of Manchester in the UK has been published in Nano Letters!

Rhombohedral graphite features peculiar electronic properties, including persistence of low-energy surface bands of a topological nature. Here, we study the contribution of electron–hole excitations toward inelastic light scattering in thin films of rhombohedral graphite. We show that, in contrast to the featureless electron–hole contribution toward Raman spectrum of graphitic films with Bernal stacking, the inelastic light scattering accompanied by electron–hole excitations in crystals with rhombohedral stacking produces distinct features in the Raman signal which can be used both to identify the stacking and to determine the number of layers in the film.

Full version of the article can be accessed here (the article is open access).


01/07/2019 - Senior Lectureship

From 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. Joshua will be moving to a postdoctoral position at the Chalmers University of Technology in Sweden.


01/05/2019 - Welcome to Will Luckin

Welcome 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 Award

I 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! 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/hBN

Our 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!

van der Waals heterostructures, vertical stacks of layered materials, offer new opportunities for novel quantum phenomena which are absent in their constituent components. Here we report the emergence of polaron quasiparticles at the interface of graphene/hexagonal boron nitride (h-BN) heterostructures. Using nanospot angle-resolved photoemission spectroscopy, we observe zone-corner replicas of h-BN valence band maxima, with energy spacing coincident with the highest phonon energy of the heterostructure, an indication of Fröhlich polaron formation due to forward-scattering electron–phonon coupling. Parabolic fitting of the h-BN bands yields an effective mass enhancement of ∼2.3, suggesting an intermediate coupling strength. Our theoretical simulations based on Migdal–Eliashberg theory corroborate the experimental results, allowing the extraction of microscopic physical parameters. Moreover, renormalization of graphene π-band is observed due to the hybridization with the h-BN band. Our work generalizes the polaron study from transition metal oxides to van der Waals heterostructures with higher material flexibility, highlighting interlayer coupling as an extra degree of freedom to explore emergent phenomena.

Full version of the article can be accessed here (subscription required).


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 Gunasekera

Surani, 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-Fuentes

Aitor 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 Nanotechnology

A 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 Thompson

With 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 Bath

It'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 Award

I have been awarded the University of Bath Excellence Award for 2013/14!


01/10/2014 - Welcome to Damien Leech

With 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 pieces

Our work in collaboration with researchers from ETH Zurich, NIMS Tsukuba and Lancaster University has been published as a cover article in Physical Review Letters!

Changing the topology of an object can significantly improve its functionality. A well-known example is changing a mug without a handle (topology of a sphere) into one with an arched handle (topology of a doughnut). In electronic materials, it is the more abstract topology of constant-energy surfaces for electrons that determines their potential for functional uses. The shape of the Fermi surface (an abstract boundary in the momentum space separating filled electron states from the empty ones) determines for example electron transport (current) or propagation of sound in a metal. Unfortunately, for bulk materials, the Fermi energy (energy of the most energetic electron in the material) cannot be easily altered to reach points in the band structure where the connectivity of the Fermi surface changes causing singular behaviour of the dependent properties.

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).