School of Physics and Astronomy

Congratulations to Davide Michieletto who has received an award from the Royal Society of Chemistry’s Statistical Mechanics and Thermodynamics Group.

The Statistical Mechanics and Thermodynamics Group currently offers this Early Career Award biennially to an exceptional scientist working in the broadly defined area of statistical mechanics and thermodynamics.

Davide’s award is for 'outstanding contributions to the field of thermodynamics and statistical mechanics, and topologically active materials inspired by DNA and genomes of living cells'.

In his short time as a researcher, Davide has built an international reputation in understanding how the topology of biological and synthetic polymers affect the macroscopic properties of complex fluids and soft materials, and has an impressive publication record. He has developed groundbreaking computer simulations of DNA-inspired material science, chromosomes and epigenetics, as well as making theoretical advances in polymer science.

Davide’s infectious passion for science and his highly interdisciplinary research projects are attracting numerous and strong students (from BSc to PhD) keen to work in this new exhilarating field at the interface of soft matter and molecular biology. 

Davide holds a Royal Society University Research Fellowship and is based in the School of Physics and Astronomy and the Institute of Genetics and Molecular Medicine.

Congratulations to Professors Ross McLure and Alex Murphy of the School of Physics and Astronomy, who today were among the 87 distinguished individuals elected to become Fellows of the Royal Society of Edinburgh.

The Royal Society of Edinburgh (RSE), Scotland’s national academy, has revealed its newly selected 2021 Fellows. These new Fellows will join the RSE’s current roll of around 1,600 leading thinkers and practitioners from Scotland and beyond, whose work has a significant impact on our nation.

Newly selected Fellows

Ross is Professor of Extragalactic Astrophysics and is based in the School’s Institute for Astronomy.  His research is focused on determining the physical properties of the first galaxies to form in the early history of the Universe. The goal of this research is to improve our understanding of the earliest phases of galaxy evolution and to unveil the sources responsible for the re-ionization of the Universe some 13 billion years ago.

On his election Ross said:

I am honoured to be joining the Fellowship of the RSE. I am looking forward to working alongside the many remarkable Fellows to promote the wide-ranging objectives of the Society.

Alex is Professor of Nuclear & Particle Astrophysics, and is based in the School’s Institute for Nuclear and Particle Physics.  His research is on direct detection of dark matter, and nuclear astrophysics, especially explosive scenarios. 

On his election Alex commented:

I feel humbled to be selected in such good company with existing RSE Fellows. I am delighted to be able to have the opportunity to support the RSE’s valuable work.

Commenting on the new fellows, Professor Dame Anne Glover, President of The Royal Society of Edinburgh said:

As Scotland’s national academy we recognise excellence across a diverse range of expertise and experience, and its effect on Scottish society. This impact is particularly clear this year in the latest cohort of new Fellows which includes scientists who are pioneering the way we approach the coronavirus; those from the arts who have provided the rich cultural experience we have all been missing, and some who have demonstrated strong leadership in guiding their organisations and communities through this extraordinary time. Through uniting these great minds from different walks of life, we can discover creative solutions to some of the most complex issues that Scotland faces. A warm welcome is extended to all of our new Fellows.

The Royal Society of Edinburgh

The Royal Society of Edinburgh, Scotland's National Academy, is an educational charity established in 1783. Unlike similar organisations in the rest of the UK, the RSE’s strength lies in the breadth of disciplines represented by its Fellowship. Its membership includes Fellows from across the entire academic spectrum – science and technology, arts, humanities, social sciences, business, and public service. New Fellows are elected to the RSE each year through a rigorous five-stage nomination process.  This range of expertise enables the RSE to take part in a host of activities such as: providing independent and expert advice to Government and Parliament; supporting aspiring entrepreneurs through mentorship; facilitating education programmes for young people, and engaging the general public through educational events.

Fellowship will help more young people develop STEM skills and learn more about the challenges of space exploration.

Congratulations to Dr XinRan Liu, who is based in the School’s Particle Physics Experiment group, and has been awarded an STFC (Science and Technology Facilities Council) Leadership Fellowship in Public Engagement. These Fellowships aim to support the very best scientists within STFC’s community, to undertake extended programmes of high quality, innovative public engagement, and to encourage and support leadership and capacity building for public engagement activities within STFC supported organisations.

Dr XinRan Liu is a particle physicist specialising in ultra-low radiation measurements, in particular the direct detection of dark matter. Building on the unusual environment in which his research is conducted, a laboratory located over a kilometre underground, XinRan has led the development of the Remote3 project, which aims to deliver much-needed STEM outreach to some of the most remote areas of Scotland. Pupils are helped to build and program miniature Mars rovers that they can then remotely operate in the underground laboratory. The fellowship will allow XinRan to expand the scope and reach of his project across Scotland, targeting young people to inform and influence their STEM career choices.

Particle physicists announce results that potentially cannot be explained by the current laws of nature.

Beyond the Standard Model

The LHCb (Large Hadron Collider beauty) Collaboration at CERN has found particles not behaving the way they should according to the guiding theory of particle physics. The collaboration includes several academics, postdocs, and students from the School’s Institute for Particle and Nuclear Physics, who play crucial roles in maintaining and operating the LHCb detector and optimising its particle identification and reconstruction algorithms.

The new result, presented to the world today at the ‘Moriond’ Particle Physics Conference, could suggest the existence of new particles not explained by the Standard Model. The Standard Model is the current best theory of particle physics, describing all the known fundamental particles that make up our Universe and the forces that they interact with. However, the Standard Model cannot explain some of the deepest mysteries in modern physics, including what dark matter is made of and the imbalance of matter and antimatter in the Universe.

Building blocks of nature

Today’s results were produced by the LHCb experiment, one of four huge particle detectors at CERN’s Large Hadron Collider (LHC). The LHC is the world’s largest and most powerful particle collider – it accelerates subatomic particles to almost the speed of light, before smashing them into each other. These collisions produces a burst of new particles, which physicists then record and study in order to better understand the basic building blocks of nature.

The LHCb experiment is designed to study particles called ‘beauty quarks’, an exotic type of fundamental particle not usually found in nature but produced in huge numbers at the LHC. Once the beauty quarks are produced in the collision, they should then decay in a certain way, but the LHCb team now has evidence to suggest these quarks decay in a way not explained by the Standard Model.

Dr Silvia Gambetta, one of the University of Edinburgh LHCb collaborators, and the experiment’s Operations Coordinator, comments:

Collecting and calibrating the data needed to perform this measurement is an effort in itself. Performing measurements like this is what makes it worthwhile for the hundreds of scientists who work every day behind the scenes.

Questioning the laws of physics

The new result relates to an anomaly that was first hinted at in 2014 when LHCb physicists spotted that beauty quarks appeared to be decaying into electrons more often than they did to muons (the muon is in essence a carbon-copy of the electron, identical in every way except that it’s around 200 times heavier.) This means that muons and electrons interact with all the forces in the Standard Model (apart from the Higgs field) with precisely the same strength, and crucially, this implies that beauty quarks should decay into muons just as often as they do to electrons. The only way these decays could happen at different rates was if some never-before-seen particles were getting involved in the decay and tipping the scales in favour of electrons.

In 2019, LHCb performed the same measurement again but with extra data taken in 2015 and 2016. This time around the result moved closer towards the Standard Model prediction, but the uncertainty on the measurement got smaller and the upshot of which was that things weren’t much clearer than they’d been five years earlier.

Today’s result adds even more data, recorded in 2017 and 2018. To avoid accidentally introducing biases, the data was analysed ‘blind’, which means that all the procedures used in the measurement had to be tested, tested and tested again before being finalised after a lengthy internal review process carried out by the 1400-strong LHCb collaboration.

Not a foregone conclusion

In particle physics, the gold standard for discovery is five standard deviations – which means there is a 1 in 3.5 million chance of the result being a fluke. This result is three deviations – meaning there is still a 1 in 1000 chance that the measurement is a statistical coincidence.

It is therefore too soon to make any firm conclusions. However, while they are still cautious, the team members are nevertheless excited by this apparent deviation and its potentially far-reaching implications.

Professor Franz Muheim, who leads the University of Edinburgh LHCb research group, and as Chair of the LHCb Editorial Board was responsible for the editorial review of the corresponding paper, said:

If confirmed this result could unveil a new fundamental interaction and lead to a complete overhaul of the Standard Model of particle physics. However, extraordinary claims need extraordinary evidence, so more measurements, also on related quantities, are required.

Next steps

It is now for the LHCb collaboration to further verify their results by collating and analysing more data, to see if the evidence for some new phenomena remains. If this result is what scientists think it is, there may be a whole new area of physics to be explored. Only time will tell if we have finally seen the first glimmer of what lies beyond our current understanding of particle physics.

By combining our knowledge of polymer physics and molecular biology, scientists can craft DNA-based soft materials that can change properties over time.

DNA is essentially a long polymer consisting of four different types of monomers – the nucleotides A, T, C and G, which stack together into base pairs. Like all polymers, DNA chains can get entangled at high concentrations. In fact, they get so tied up that a single human cell can store up to 2m of DNA crammed into its nucleus, an object just 10μm in size.

If DNA molecules stayed horribly entangled, there would be a problem: it would be impossible for chromosomes – long pieces of DNA containing millions of base pairs – to be constantly read and copied. And if that didn’t happen, cells would be unable to make proteins and multiply. Nature has got round this problem by “engineering” special proteins that can change DNA’s shape, or “topology”, to get rid of the entanglements.

Dr Davide Michieletto, who is based in the School’s Institute for Condensed Matter and Complex Systems claims that DNA’s ability to morph its architecture means that it behaves a bit like soap:

The link between DNA and soap is certainly surprising. But by combining our knowledge of polymer physics and molecular biology, we can exploit this soapy feature to craft DNA-based soft materials that change topology over time. And by tweaking their topology, we can control their physical properties in unusual ways.

Soaps consists of “amphiphilic” molecules, one part of which loves water and another part that hates it. These molecules don’t exist in isolation but group together to form structures, known as “micelles”. At low concentrations, they are usually spherical, but at higher concentrations, the molecules can form long, tube-like structures, with the water-hating parts of the molecules facing inside.

These elongated, multi-molecule objects do strange things at high concentrations. In particular, just like DNA, they get entangled, increasing the fluid’s friction and making it harder to deform. In fact, the entanglements between worm-like micelles are what give soap, shampoo, face cream or hair gel that pleasant, smooth hand-feel.

Just like DNA, worm-like micelles can also disentangle themselves by constantly getting broken up and glued back together again with a new topology. But there’s one big difference: the DNA inside cells needs to preserve its genetic sequence otherwise cells might die or diseases could be triggered. In soap, there’s no precise sequence of monomers in micelles so they can be put back together in any order. This has a fundamental impact on how topological operations are performed on DNA: they have to happen at the right place and the right time.

To break DNA you need “restriction enzymes”, which cut the chain only where a certain DNA sequence is recognized. Topoisomerase proteins, meanwhile, have to be precisely positioned at certain locations on chromosomes where entanglements and mechanical stress often accumulate. Similarly, when two pieces of DNA reconnect and recombine – the process is tightly regulated in space and time to avoid aberrant chromosomes in cells. It’s almost as if DNA (thanks to proteins) behaved as a smart worm-like micelle.

Davide is definitely not the only person to see the potential of DNA as an advanced polymer, rather than just as genetic material. Over the last two decades, researchers have developed lots of new, DNA-based materials, such as hydrogels and nano-scaffolds, that could, for example, grow bones, tissues, skin and cells, using the unique properties of DNA to encode information.

What excites me about this line of research is that solutions of DNA, functionalized by the presence of proteins that can change DNA’s topology in time, may yield novel “topologically active” complex fluids that respond to external stimuli. For example, adding restriction enzymes that can cut the DNA at specific sequences could allow stiff and robust DNA-based scaffolds to be degraded as soon as they are no longer needed.

At the same time, adding topoisomerase to an ensemble of DNA plasmids (circular DNA) can create a gel, in which the rings of DNA are joined together like the rings on the logo of the modern-day Olympic Games. These “Olympic gels” have proved very difficult to synthesize chemically in the lab despite decades of trying, yet nature has been doing so for millions of years.

Apart from their intrinsic scientific interest, studying such biological structures will also help scientists design a new generation of self-assembled topological materials. These complex, DNA-based materials hold great technological promise, but to make progress, multidisciplinary teams of physicists, chemists and biologists are required.

Davide adds:

We still need more top-quality journals that recognize high-value interdisciplinary research of this kind, while research centres that cut across traditional academic disciplines will be vital too. It is an exhilarating field to be in, where everyone – no matter where they are in their career – learns something new every day. My hope is that in 10 or 20 years’ time, scientists who are starting out in their careers will no longer feel obliged to explore only one specific discipline or to choose between theoretical and experimental work. Instead, it would be great if they could simply satisfy their scientific curiosity no matter what background they are from. For if they do that, who knows what we might find next?

Using theoretical and experimental analysis, researchers aim to better understand the novel and intriguing magnetic properties of 2D materials for the next generation of information technologies.

Since the discovery of graphene in 2004 - which won its inventors the Nobel Prize and launched a new field of materials research - two dimensional (2D) materials that are one atom thick have promised to revolutionized technology as a result of their unique and sometimes bizarre properties.

However, one crucial property to data storage and electronics has, for a long time, remained elusive in these materials: magnetism.

For a while, many experts thought that 2D magnetism existed only in theory, but in 2017, a breakthrough came with the first measurements of ferromagnetism were made in chromium triiodide (CrI₃) and Cr₂Ge₂Te₆ compounds. This discovery sparked a renewed interest in the magnetism of these materials, for which many unknowns still remain. "For one," said Dr Elton Santos from the School of Physics and Astronomy, "it is still unclear how magnetism develops in 2D."

Dr Santos is part of a collaborative team of researchers who suggest that as a result of magnetic domains found in 2D CrI₃, this material shows properties that may go beyond those in conventional magnets, with quantum effects playing an important role in large area and denser amounts of information that may be stored. The researcher’s findings have recently featured the cover of Advanced Materials.

The interplay between different interactions usually align the spins of the atoms in small spatial regions on the material, with different orientations forming what are called ‘magnetic domains’. In the case of monolayer CrI₃, however, we observed that the domains cluster themselves in patches that can be large enough to cover the material’s entire surface, like in a single-domain particle but with no magnetic fields. Materials that show such a large area of magnetism can be used in different magnetic processes, such as information storage, but in a much finer fashion—in an area about 10,000 times thinner than the human hair.

When first discovered in 2017, 2D materials like CrI₃ were initially classified as Ising magnets, which is the simplest mathematical model that may describe magnets in a honeycomb lattice of spins, where each site can be either spin up or spin down. Each spin acts like a mini magnet with its own magnetic moment; if all the spins are aligned, then the whole lattice behaves like a big magnet with a net magnetic moment.

But Santos and his colleagues felt this classification did not fully capture the properties of these materials, as they had observed some contradictory phenomenon.

CrI3 was assigned as an Ising magnet, but at the same time it shows properties that would not be compatible with this characteristic, i.e., spin-waves—continuous variations of the orientation of the spins in a wave form. Spin waves have been measured by different techniques, including neutron scattering and Raman spectroscopy, and by different groups worldwide. So, we thought something was not quite right.

What Santos and his group uncovered is the presence of domain walls within the 2D materials, which evolve following the low-dimensionality of the layer, which is not commonly found. To give an example, in conventional magnets like Fe (iron), the domain walls just separate the magnetic domains but they don’t change. They are mostly static in time.

The team now is working on the implementation of these thin magnets in different device-platforms. For instance, where the control of magnetic domain walls is mediated by electrical currents. Initially designed by Stuart Parkin and his team at IBM in 2008, this phenomenon was used to build what are called racetrack memories, which organize data in a 3D microchip and may someday replace conventional data storage.

Dr Santos commented:

We believe that the implementation of our findings in racetrack structures is a matter of time. Since the domain wall is very narrow in these 2D magnets, it is ideal for such processes, and they can also be transferred on different surfaces which facilitates integration with current semiconductor components. This could result in devices that are practically unbreakable because the 2D material is so flexible, as well as light and thin enough to be carried around in your pocket but with the capacity to store thousands of huge files on the go. However, we would need to be cautious since there is a long way before we will reach that level in terms of application.

Attend Postgraduate Virtual Open Days to find out about our MSc programmes.

The School of Physics & Astronomy will take part in the University of Edinburgh Postgraduate Virtual Open Days 23-25 March 2021. 

Academic and professional staff together with students will be involved in a number of online information sessions.

MSc programme

Presentations and Q&A sessions

• Tuesday 23rd March: Introduction to MSc Theoretical Physics and Mathematical Physics 11:00-12:00 UK time
• Tuesday 23rd March: Introduction to MSc Particle and Nuclear Physics  13:00-14:00 UK time
• Wednesday 24th March: Introduction to MSc Theoretical Physics and Mathematical Physics  16:00-17:00 UK time, repeat of the Tuesday session

Exhibitor booths

• Tuesday 23rd March: text chat live with a member of School's recruitment team 15.00-17.00 UK time
• Thursday 25th March: text chat live with a member of School's recruitment team 9.00-11.00 UK time

To book a place visit the Virtual Postgraduate Open Days 2021 page on the University of Edinburgh website.

The Remote3 project based at the University of Edinburgh was invited by the Muslim Scout Fellowship to run a space night for their scouts (aged 10-14 years), with the aim of achieving the Scout Astronautics Activity badge.

The Remote³ project, or ‘Remote sensing by remote schools in remote environments’, is an STFC (Science and Technology Facilities Council) Spark Award Project aiming to deliver much-needed STEM outreach to some of the most remote areas of Scotland.

The Remote³ team worked with the Muslim Scout Fellowship to complete one requirement of the Astronautics Activity Badge - debate about life elsewhere in the universe. Along with team members from the Rutherford Appleton Laboratory and the Boulby Underground Laboratory we discussed what alien life might it look like. How do we search for life on other planets and moons? And how would the human race react to the discovery of life elsewhere in the universe? 

The evening was broadcast live to social media, generating close to 1000 comments and questions during the event, and garnering more than 8000 views since. All attendees were able to complete the badge requirement.

The Remote³ project will continue to work closely with the Muslim Scout Fellowship in future events, including their 2022 summer Jamboree, as well as with many other public engagement teams across Scotland, the UK and beyond.

Scientists are developing vital software to exploit the large data sets collected by the next-generation experiments in high energy physics (HEP), predominantly those at the Large Hadron Collider (LHC).

Over the years, the existing code has struggled to meet rising output levels from large-scale experiments. The new and optimised software will have the capability to crunch the masses of data that the LHC at CERN and next-generation neutrino experiments such as DUNE (Deep Underground Neutrino Experiment) and Hyper-Kamiokande will produce this decade.  

The project, known as SWIFT-HEP (SoftWare InFrastructure and Technology for High Energy Physics), involves the School’s Particle Physics Experiment researchers Professors Peter Clarke, Philip Clark, Sinead Farrington, Christos Leonidopoulos and Drs Yanyan Gao, Akanksha Vishwakarma and Ben Wynne. This work is in collaboration with a number of universities across the UK, partners from the Science and Technology Facilities Council’s (STFC) Rutherford Appleton Laboratory, and in co-operation with CERN and other international stakeholders.

As part of a precursor project to SWIFT-HEP, Professor Farrington, Dr Vishwakarma and UK colleagues coordinated a workshop on Efficient Computing in High Energy Physics where the community met to formulate ideas and plans for the future and to engage with industry invitees. Professors Clarke and Farrington are members of the Advisory Board which led to the eventual SWIFT-HEP proposal. 

If scientists used everyday computers to store one exabyte of data they would need almost one million powerful home computers to do it. Without a software upgrade the need of computing resources for the LHC would be expected to grow six times in size in the next decade. This is not only too expensive in hardware costs and software inefficiencies, but would also imply an increased consumption of electricity. The more efficient software the team will develop will help reduce the usage of computing resources and the carbon footprint of data centre across the world. The project is to ensure scientists can exploit the physics capabilities of future HEP experiments, while keeping computing costs affordable.

The project’s key milestone for 2024 is to evolve from proof-of-concept studies to deployment, ready for the start of data-taking at the HL-LHC and next generation neutrino experiments, which are expected to dominate the particle physics scene in the second half of the decade.

Merons are a type of topological spin texture, with relevance for both fundamental and technological problems. In this theoretical work, scientists show that a new family of van der Waals (vdW) CrCl3 ferromagnet can host merons and anti-merons, and goes on to explore their dynamics and interactions.

Magnetic moments in magnetic materials can organise themselves in different forms of spin structures. From usual ferromagnetic and anti-ferromagnetic materials where spins of neighbouring atoms tend to align parallel or antiparallel to each other, respectively, up to more intricate configurations where spins can assume complex orientations composing a quasiparticle on their own (Figure 1). 

Such spin quasiparticles hold promises in several aspects of information technologies from cheaper, lighter devices, up to ultra-compact spin-based electronic (spintronics). In particular, these quasiparticles offer energy-efficient current-driven phenomena useful in the next generation of low-energy device applications (i.e. computer memory, logic, etc.). Despite their importance, direct observation of spin textures, such as merons and anti-merons, is rare and has been limited to femtosecond transient states, and a few complex chiral magnets. On a recent paper led by the School’s Dr Elton Santos published in Nature Communications, and featured at the Editor’s Highlight section, reports evidence that recently exfoliated vdW CrCl₃ hosts merons and antimerons in its magnetic structure. This finding may revolutionise how to integrate fundamental spin-textures in two-dimensional device platforms. 

The concept of merons and antimerons originated in classical field theory dated from the 1970s, and later applied to particle physics, and more recently in condensed matter physics. In merons and antimerons, which are also called vortex and antivortex, the spins at the core region point either up or down, but those around the perimeter align parallel to the plane of the material with a gradual variation of the orientation of the spins as they move towards or backwards the centre (Figure 1).  Some studies have confirmed the existence of merons and antimerons in chiral magnets, but their complex chemistry and synthesis require additional protocols that ramp up further progress. With the discovery of meron quasiparticles in a relatively simpler vdW layered material, it opens the prospect of explorations of a number of other 2D magnets where such spin textures could be observed. Indeed, the researchers also give some guidelines for looking into materials that may develop topological non-trivial spin textures such as weak out-of-plane anisotropy, and potential competitions between next-nearest neighbour interactions. With the discovery of graphene in 2004 via a handy scotch-tape exfoliation technique, different nanosheets have been isolated up to date. This has generated a broad and fast-pace increased library of 2D compounds for applications. Similar methods have been applied to layered magnetic materials which have contributed to rapidly popularise the field.

The multiscale theoretical methods developed also provide a general framework for a rapid computational screening ahead of lab experimentation on compounds that may stabilise merons and antimerons. The authors unveil the complete evolution of these spin quasiparticles from pair creation, their subsequent motion over magnetic domains (Figure 2), and annihilation via collisions. These results push the boundary to what is currently known about the most concise and fundamental localized spin structures in 2D magnets and open exciting opportunities to explore magnetic domain control via topological spin textures.