New frontiers in topological materials

Theo Murphy meeting organised by Professor Robert-Jan Slager, Dr Nur Ünal and Professor Bartomeu Monserrat
Topological materials are an active area of research in all physical sciences. Motivated by the recent synergy with quantum geometry, this meeting will serve as a contemporary event to discuss state-of-the-art advances in theory and experiments. Connecting experts from across condensed matter physics, materials science, and quantum simulators, these discussions will identify novel future research avenues.
Programme
The programme, including the speaker biographies and abstracts, will be available soon. Please note the programme may be subject to change.
Poster session
There will be a poster session on Monday 23 June 2025. If you would like to present a poster, please submit your proposed title, abstract (up to 200 words), author list, and the name of the proposed presenter and institution to the Scientific Programmes team. Acceptances may be made on a rolling basis so we recommend submitting as soon as possible in case the session becomes full.
The deadline for submissions is 10 June 2025. Submissions made after this date may not be included in the programme booklet.
Attending this event
- Free to attend and in-person only
- When requesting an invitation, please briefly state your expertise and reasons for attending
- Requests are reviewed by the meeting organisers on a rolling basis. You will receive a link to register if your request has been successful
- Catering options will be available to purchase upon registering. Participants are responsible for booking their own accommodation. Please do not book accommodation until you have been invited to attend the meeting by the meeting organisers
Enquiries: contact the Scientific Programmes team.
Organisers
Schedule
08:55-09:00 |
Welcome by the Royal Society and lead organiser
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09:00-09:45 |
How to measure the quantum geometry of Bloch electrons in solids?
Understanding the geometric properties of quantum states and their implications in fundamental physical phenomena is at the core of modern physics. The Quantum Geometric Tensor (QGT) is a central physical object in this regard, encoding complete information about the geometry of the quantum state. The imaginary part of the QGT is the well-known Berry curvature, which plays a fundamental role in the topological magnoelectric and optoelectric phenomena. The real part of QGT is the quantum metric, whose importance has come to prominence very recently, giving rise to a new set of quantum geometric phenomena, such as anomalous Landau levels, flat band superfluidity, excitonic Lamb shifts, and nonlinear Hall effect. Despite the central importance of the QGT, its experimental measurements have been restricted only to artificial two-level systems. In this talk, I am going to present two recent progresses in QGT measurement of Bloch states in solids. First, I will proposed a general method to extract the QGT by introducing another geometrical tensor, the quasi-QGT, who components, the band Drude weight and orbital angular momentum, are experimentally accessible and can be used for extracting the QGT. In the second part, I will report the first direct measurement of the full quantum metric tensors using black phosphorus as a representative material. The key idea is to extract the momentum space distribution of the pseudospin texture of the valence band from the polarisation dependence of angle-resolved photoemission spectroscopy measurement. ![]() Professor Bohm Jung YangSeoul National University, South Korea ![]() Professor Bohm Jung YangSeoul National University, South Korea Professor Bohm Jung Yang is a theoretical condensed matter physicist interested in the study of emergent physics in quantum materials with nontrivial topology and correlative effect. He is interested in (1) the symmetry-based classification of topological phases, (2) the unconventional topological phase transitions and critical phenomena, (3) the search of novel topological superconductors, and (4) the quantum geometry driven physical properties in quantum materials. |
09:45-10:30 |
What (is/isn't) topology and geometry
![]() Professor Steven SimonUniversity of Oxford, UK ![]() Professor Steven SimonUniversity of Oxford, UK Steven H Simon is an American theoretical physics professor at Oxford University and a professorial fellow of Somerville College, Oxford. Before coming to Oxford he was director of theoretical physics research at Bell Laboratories. He has served on the UK EPSRC Physical Sciences Strategic Advisory Board. He is know for his work on Topological Phases of Matter, Topological Quantum Computation, and Fractional Quantum Hall Effect. He is the author of a popular introductory book on solid state physics, entitled "The Oxford Solid State Basics" and a new book on "Topological Quantum". |
10:30-11:00 |
Break
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11:00-11:45 |
Title to be confirmed
![]() Professor Jacqueline BlochFrench National Centre for Scientific Research, France ![]() Professor Jacqueline BlochFrench National Centre for Scientific Research, France Jacqueline Bloch is Director of Research at the CNRS, Associate Professor at the Ecole and member of the French Academy of Sciences. She is an experimental physicist, expert in semiconductor physics, light matter interaction, quantum and nonlinear optics and develops her research at the Centre for Nanosciences and Nanotechnologies in Palaiseau. Making use of quantum fluids of polaritons in lattices of coupled microcavities, she is currently exploring topological photonics and the physics of open Bose Einstein condensates. |
11:45-12:30 |
Fractional quantization in nonlinear optical Thouless pumps
I will present my group's recently experimental work on the fractional pumping of solitons in nonlinear Thouless pumps, using waveguide arrays. Specifically, I will show that the displacement (in unit cells) of solitons in Thouless pumps is strictly quantized to the Chern number of the band from which the soliton bifurcates in the low power regime; whereas in the intermediate power regime, nonlinear bifurcations lead to fractional quantization of soliton motion. This fractional quantization can be predicted from the multi-band Wannier functions associated with the states of the pump. ![]() Professor Mikael RechtsmanPennsylvania State University, USA ![]() Professor Mikael RechtsmanPennsylvania State University, USA Mikael Rechtsman is a Professor of Physics at Pennsylvania State University in the USA, and currently the visiting QuantAlps professor of physics at the Néel Institute of the CNRS in Grenoble, France. His research group carries out both experimental and theoretical research in nonlinear, quantum and topological photonics. He is perhaps best known for the first demonstration of a topological insulators for light. |
13:15-14:15 |
Poster session
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14:15-15:00 |
Topology and chirality
Topology, a well-established concept in mathematics, has nowadays become essential to described condensed matter. At its core are chiral electron states on the bulk, surfaced and edges of the condensed matter systems, in which spin and momentum of the electrons are locked parallel or anti-parallel to each other. Magnetic and non-magnetic Weyl semimetals for example, exhibit chiral bulk states that have enabled the realisation of predictions from high energy and astrophysics involving the chiral quantum number, such as the chiral anomaly, the mixed axial-gravitational anomaly and axions. The potential for connecting chirality as a quantum number to other chiral phenomena across different areas of science, including the asymmetry of matter and antimatter and homochirality of life, brings topological materials to the fore. ![]() Professor Claudia FelserMax Planck Institute for Chemical Physics of Solids, Germany ![]() Professor Claudia FelserMax Planck Institute for Chemical Physics of Solids, Germany Claudia Felser studied chemistry and physics at the University of Cologne, completing her diploma in solid state chemistry (1989) and her doctorate in physical chemistry. After postdoctoral fellowships at the Max Planck Institute in Stuttgart (Germany) and the CNRS in Nantes (France), she joined the University of Mainz in 1996 as an assistant professor. In 2003, she became a full professor at the University of Mainz and is currently the Director of the Max Planck Institute for Chemical Physics of Solids in Dresden. Claudia Felser in a fellow of the IEEE Magnetic Society, American Physical Society, and Institute of Physics. She is a member of the Leopoldina, the Germany National Academy of Sciences, and acatech, the German National Academy of Science and Engineering. Her research focuses on the design and synthesis, and physical characterisation of new quantum materials, particularly Heusler compounds and topological materials for energy conversion and spintronics. She was inducted into the Hall of Fame of German Research in 2023, and has received several prestigious awards, including the Liebig Medal of the German Chemical Society, the Max Born Prize of DPG and IOP, and the APS James C McGroddy Prize, and the Von Hippel Award. |
15:00-15:30 |
Break
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15:30-16:15 |
Quantum geometry and superconductivity
We have found that superconductivity and superfluidity are connected to quantum geometry: the superfluid weight in a multiband system is proportional to the minimal quantum metric of the band. The quantum metric is connected to the Berry curvature, which relates to superconductivity to the topological properties of the band. Using this theory, we have shown that superconductivity is also possible in a flat band where individual electrons would not move. These results may be relevant for explaining the observation of superconductivity in twisted bilayer graphene. The quantum transport in a flat band shows unique behaviour: while supercurrent can flow, quasiparticle transport is highly suppressed even in non-equilibrium conditions. This may have important consequences for superconducting devices. We have predicted that flat band systems as part of Josephson junctions can lead to behaviour distinct from the dispersive case. We have also found that quantum geometry governs Bose-Einstein condensates in flat bands. While most of the mentioned work is for on-site interactions, in a recent study we found that nearest-neighbour pairing at flat band and van Hove singularities of the kagome and Lieb lattices is strongly influenced by the geometric properties of the eigenfunctions, and it is crucial to determine the superfluid weight of the superconducting and pair density wave orders as it may contradict the predictions by pairing susceptibility. ![]() Professor Päivi TörmäAalto University, Finland ![]() Professor Päivi TörmäAalto University, Finland Päivi Törmä is a professor in the Department of Applied Physics, Aalto University, Finland, and has a MSc degree from the University of Oulu, Finland, a Master of Advanced Study degree from the University of Cambridge, UK, and a PhD in 1996 from the University of Helsinki. Her research ranges from theoretical quantum many-body physics to experiments in nanophotonics. Her work has revealed a new connection between quantum geometry and superconductivity that explains why flat bands can carry supercurrent, which is essential in the search for superconductors that work at high temperatures. In her experiments, Päivi has worked on the strong coupling of surface plasmon polariton modes and molecules and her group succeeded in realising the first plasmonic Bose-Einstein condensate. |
16:15-17:00 |
Exploring the dynamics of quantum mass phases of matter on quantum processors
Quantum fluctuations and interactions give rise to exotic phases of matter with remarkable properties, pushing the boundaries of our understanding of man-body quantum systems. Solving these problems is notoriously difficult on classical computers due to the exponential complexity of quantum many-body physics. Quantum processors, however, open new avenues for exploring these systems, offering a direct and potentially transformative approach. In this talk, we will first discuss recent progress in realising and visualising dynamics of charges and strings in (2+1)D lattice gauge theories. We will then investigate a class of novel, highly entangled quantum phases that exist only in non-equilibrium settings and demonstrate how to probe their stability using a quantum processor. ![]() Professor Frank PollmannTechnical University of Munich, Germany ![]() Professor Frank PollmannTechnical University of Munich, Germany Professor Pollmann's research focuses on a variety of problems in the field of condensed matter theory. His main focus lies on the study of collective phenomena which arise due to quantum mechanical effects in systems of correlated particles. Areas of research include the study of topological phases of matter, frustrated spin systems, and the dynamics of disordered systems. To gain deeper insights into the physics of these systems, he employs concepts from quantum information theory. These concepts have proven to be very useful in acquiring a fundamental understanding of the structure of quantum many-body states and in designing efficient computer algorithms for numerical simulations of correlated quantum systems. |
09:00-09:45 |
Title to be confirmed
![]() Professor Maia VergnioryUniversité de Sherbrooke, Canada ![]() Professor Maia VergnioryUniversité de Sherbrooke, Canada Maia Vergniory is a Basque computational physicist and senior researcher at the Donostia International Physics Centre (DIPC) in San Sebastián, Spain, as well as a Professor at the Université de Sherbooke in Canada. Her research pioneers the theory and discovery of topological materials - crystals whose surface states conduct electricity robustly while the bulk remains insulating - using high-throughput ab initio calculation and the Topological Quantum Chemistry framework to classify and predict new compounds. Her work has earned her the 2017 L'Oréal-UNESCO For Women in Science Award, in 2019 the Ikerbasques Foundation award and was elected as a Fellow of the American Physical Society in 2022. In 2023 she received the Canadian Excellence Research Chair. |
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09:45-10:30 |
Interplay of topology, quantum geometry and nonlinear transport to detect hidden symmetry breaking in emerging quantum materials
Phase transitions in solids are often accompanied by structural and/or spin order changes. Subtle lattice distortions, for example, can remain hidden from conventional crystallographic probes, hindering the identification of the correct order parameter. I will demonstrate an extremely sensitive metrology for identifying hidden symmetry breaking in complex quantum materials through the interplay of topology, quantum geometry, and nonlinear quantum transport. I will introduce our theoretical and experimental results on a correlated polar metal Ca3Ru2O7 (hidden structural transition) and an antiferromagnetic semiconductor CrSBr (hidden spin transition). ![]() Professor Binghai YanPennsylvania State University, USA ![]() Professor Binghai YanPennsylvania State University, USA Binghai Yan is a theoretical physicist studying quantum materials, including topological materials and chiral materials, at the Pennsylvania State University. After completing his PhD at Tsinghua University in 2008, he worked as a Humboldt postdoc at Bremen University and later at Stanford University. He was a group leader in the Max Planck Institute in Dresden during 2012 – 2016, assistant and associate professor at Weizmann Institute during 2017 – 2024. He joined the Penn State University as a professor of physics in 2025. He was awarded the ARCHES Prize in Germany in 2013, the Israel Physical Society Prize for Young Scientist in 2017 and recognised as a Highly Cited Researcher every year since 2019. |
10:30-11:00 |
Break
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11:00-11:45 |
Quantum simulation of frustrated and topological materials, and of mesoscopic physics, using ultracold atoms
I will present three experiments in the making where we hope to employ ultracold atoms to explore interesting phenomena in condensed-matter and mesoscopic physics. First, I will summarise recent work on transport properties of ultracold atoms within triangular two-dimensional lattices, highlighting effects of geometric singularities at band-touching points and of geometric frustration of atomic motion in flat bands. I will update you on recent efforts to place ultracold Fermi gases in such lattices. Second, I will describe how we hope to use ultracold transition-metal atoms to realise novel states of matter such as topological superfluids, and will present experimental progress in cooling titanium atoms for this purpose. Last, I will describe experiments using atoms trapped in optical tweezer arrays where we return to the study of symmetry breaking transitions related to the Dicke model, but, now, with digital control over the atom number in a distinctly mesoscopic regime. ![]() Professor Dan Stamper-KurnUniversity of California, Berkeley, USA ![]() Professor Dan Stamper-KurnUniversity of California, Berkeley, USA Dan Stamper-Kurn is a Professor of Physics at the University of California, Berkeley, and also a Faculty Scientist in the Materials Sciences Division of Lawrence Berkeley National Laboratory. Together with his research team at Berkeley, Professor Stamper-Kurn is an experimentalist who studies quantum mechanical phenomena in systems composed of ultracold atoms and quantum states of light. Current areas of interest include quantum simulation of geometrically frustrated materials and other condensed-matter systems, symmetry breaking dynamics in mesoscopic systems composed of a small number of atoms, quantum information processing in the neutral-atom platform, and bringing new atomic elements to the ultracold temperature regime. Professor Stamper-Kurn initiated and now directs the Challenge Institute for Quantum Computation, a collaboration centred at several universities across California, which focuses on fundamental scientific and engineering challenges in quantum information science. |
11:45-12:30 |
Topology in complex optical lattices
Ultracold atoms in optical lattices are one of the major platforms for experimental quantum simulations and many-body physics, including topology. One particularly useful feature of ultracold atoms is the possibility to employ Bose-Einstein condensates as very localised probes in momentum space. I will start by reviewing our previous work on using atom interferometry to directly measure Berry flux in a graphene-type hexagonal optical lattice, where we could directly detect the topologically protected Berry flux associated with a Dirac point. Beyond single bands, the resulting Berry phases generalise to matrix-valued Wilson loops, which give rise to even richer physics. I will present out current status towards applying these methods to study the multiband topology and Euler class in the Kagome lattice. In a second part, I will discuss how quasiperiodic potentials such as the Aubry-André-Harper chain can give rise to a fractal band structure where each effective band can support topologically protected quantised charge pumping. Surprisingly, the quantised currents are extremely robust and remain quantised even when additional disorder closes the relevant gaps. ![]() Professor Ulrich SchneiderUniversity of Cambridge, UK ![]() Professor Ulrich SchneiderUniversity of Cambridge, UK Professor Ulrich Schneider is an experimental physicist studying quantum simulation and many-body physics using ultracold atoms in optical lattices. He is a reader in many-body physics at the Cavendish Laboratory of the University of Cambridge and a fellow of Jesus College Cambridge. Earlier positions include the Ludwig-Maximilians Universität in Munich and the Johannes-Gutenberg Universität in Mainz. He has worked extensively on non-equilibrium dynamics in optical lattices and the realisation of many-body localisation. Other works include studies of quantum transport, the dynamics of a quantum phase transition, fermionic Mott insulators, and Negative Absolute Temperatures. He also developed interferometric probes for topology and realized optical quasicrystals. He is the winner of the 2015 Rudolf-Kaiser prize, holds an ERC starting grant, and is part of the AION consortium, the DesOEQ programme grant and the UK Quantum Technology Hub in Computing & Simulation. |
13:30-14:15 |
Majorana-metal transition in a disordered superconductor: percolation in a landscape of topological domain walls
Most superconductors are thermals insulators. A disordered chiral p-wave superconductor, however, can make a transition to a thermal metal phase. Because heat is then transported by Majorana fermions, this phase is referred to as a Majorana metal. We will discussion numerical evidence that the mechanism for the phase transition with increasing electrostatic disorder is the percolation of boundaries separating domains of different Chern number. We construct the network of domain walls using the spectral localiser as a "topological landscape function", and obtain the thermal metal insulator phase diagram from the percolation transition. ![]() Professor Carlo BeenakkerLeiden University, The Netherlands ![]() Professor Carlo BeenakkerLeiden University, The Netherlands Carlo Beenakker is a theoretical physicist at the Instituut-Lorentz of Leiden Univrsity, where he studies topological states of matter, in particular in view of applications to quantum computing. He is a member of the Royal Netherlands Academy of Arts and Sciences, and a Knight in the order of the Dutch Lion. |
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14:15-15:00 |
Ideal optical flux lattices
Cold atomic gases have the potential to explore bosonic version of fractional quantum Hall states. To achieve such phases, it is of interest to generate optical lattices that host Chern bands with narrow energy dispersion and certain geometric properties which promote the realisation of strongly correlated phases. One approach is to use Raman coupling of internal (spin) states to form optical flux lattices that are analogous to Landau levels. I shall present recent results which show how one can design optical flux lattices to make them both very narrow in energy and of "ideal" geometry. ![]() Professor Nigel CooperUniversity of Cambridge, UK ![]() Professor Nigel CooperUniversity of Cambridge, UK Nigel Cooper received a DPhil from the University of Oxford in 1994. He held research positions at Harvard University and the Institut Laue Langevin, and was a Royal Society University Research Fellow and Lecturer at the University of Birmingham before moving to Cambridge in 2000. He was awarded the 2007 Maxwell Medal and Prize by the Institute of Physics, a Humboldt Research Award (2013), an EPSRC Established Career Fellowship (2013), a Simons Investigator Award (2017) and the 2019 Lord Rayleigh Prize of the IOP. |
15:00-15:30 |
Break
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15:15-16:00 |
Quantum geometry of correlated electrons and their optical signatures
Recent experiments of transition-metal dichalcogenide moiré heterostructures have highlighted the intricate interplay between strong electronic correlations, topology and Bloch band geometry in highly tunable systems. Thus far, its understanding rests on mappings to Landau levels and the fractional quantum Hall effect, while competing and time-reversal-symmetric phases due to nontrivial quantum geometry remain largely unexplored. In this talk, I will first describe how strong interactions in fractionally filled time-reversal-symmetric bands can realise a new class of topological Mott insulators on emergent Kondo lattices, with possible realisations in twisted MoTe2 and WSe2. These phases feature an interaction-driven segregation of the active topological bands into a partial Wannier basis of localised magnetic orbitals as well as itinerant topological states, closely resembling Kondo systems, albeit with a topological twist. I will then argue that the interplay of quantum geometry and electronic interactions can be diagnosed via low-frequency optical conductivity measurements of correlated metals. At dilute fillings near a topological band inversion, a quantum-geometric Fermi surface contribution can lead to drastically enhanced terahertz optical absorption and enrich the physics of Fermi liquids. ![]() Professor Martin ClaassenUniversity of Pennsylvania, USA ![]() Professor Martin ClaassenUniversity of Pennsylvania, USA Martin Claassen is a condensed matter theorist at the University of Pennsylvania. His research focuses on the emergent collective phenomena of quantum materials in and far from thermal equilibrium, and the interactions of light and matter. After obtaining a PhD at Stanford University in 2017, he worked as a postdoctoral research fellow at the Center for Computational Quantum Physics of the Simons Foundation Flatiron Institute in New York. Since 2020, he is an assistant professor in the Department of Physics and Astronomy at the University of Pennsylvania. |
16:00-16:45 |
Aspects of localisation in driven matter
Localisation, or its absence, is a fundamental distinguishing feature of any many-body system, affecting the ways that mass, charge, energy, and momentum move and respond to inhomogeneity. A current frontier in this venerable field is the study of transport in driven matter: subjecting a quantum system to a time-dependent Hamiltonian can generated a rich array of localising and delocalising dynamics. I will discuss results from a sequence of recent cold-atom experiments on kicked and driven quantum matter, highlighting data on anomalous transport, the interplay between dynamical and disorder-induced localisation, and quantum simulation of integer quantum Hall matter illuminated by light of arbitrary polarisation. The chiral nature of the latter experiment enables drive-synthesised topological phenomena and opens pathways to spectroscopic probes of the quantum geometry of higher-dimensional systems with lower-dimensional ones. In a surprise pivot to practical applications, I will close with a brief description of how Floquet band engineering, a celebrated tool for synthesising topological quantum matter, can also be used to build compact precise force sensors based on matter-wave interferometry. ![]() Professor David WeldUniversity of California, Santa Barbara, USA ![]() Professor David WeldUniversity of California, Santa Barbara, USA David received a BA in physics from Harvard University and a PhD in physics from Stanford University; after working as a postdoctoral researcher and research scientist at MIT he joined the faculty at UC Santa Barbara. Current research interests of the Weld group include quantum and classical transport, Floquet phases of matter, quasicrystals, and quantum interactive dynamics. The Weld group's research in experimental ultracold atomic physics has been recognised with an NSF CAREER award, a Presidential Early Career Award for Scientists & Engineers (PECASE), a Sloan Fellowship, a Young Investigator Prize form the Air Force Office of Scientific Research, and an Experimental Physics Investigator award from the Moore Foundation. David is currently a visiting scholar in Jesus College at Cambridge University. |
16:45-17:00 |
Panel discussion
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