What’s the matter with condensed matter? Getting past the relative obscurity of solid-state physics in the public eye

08 Aug 2023

From the macroscopic to the microscopic physical properties of the world around us, condensed-matter and materials-science research have a huge impact on daily life. And yet, as James Kakalios highlights, the field remains on the periphery of popular-physics outreach – especially compared to astronomy and big science

Condensed matter everywhere Semiconductor wafers are divided up into blocks to make the integrated circuits, or chips, used in electronic devices. Hundreds of thousands of transistors can be fitted on a single chip and connected by conducting pathways. (Courtesy: Alfred Pasieka/Science Photo Library)

In 2022 we celebrated the 75th anniversary of the development of the first transistor and today it is estimated that there are more than three billion trillion of these devices in use around the world. Without the semiconductor transistor, there would be no mobile phones (smart or otherwise) and no personal computers either. Indeed, most of the devices you’d find in a doctor’s office or hospital (just think of the data processing necessary to generate an MRI image) wouldn’t exist, and you’d be hard-pressed to get your car to start each morning.

Solid-state and semiconductor physics, it’s fair to say, have transformed the world we live in. Promising research in quantum computation and graphene-based devices suggests that solid-state physics will continue to have a large impact on our daily life. That’s why it’s surprising, to me at least, that there is so little public engagement and outreach centred on condensed-matter physics.

Visit the science section devoted to physics in any bookstore and you’ll find the shelves groaning under the weight of books on a variety of topics in astronomy and cosmology – everything from string theory and dark matter to black holes and gravitational waves – as well as books on particle physics and quantum mechanics. But there are significantly fewer popular-science books describing solid-state and materials-science research.

Let me be clear: I am not saying that there shouldn’t be popular science books, news articles and television programmes devoted to astronomy or particle physics. The accomplishments of the Large Hadron Collider (LHC), Laser Interferometer Gravitational-Wave Observatory (LIGO) and the James Webb Space Telescope (JWST), to name just a few, are truly inspiring and should be widely shared with the general public. These projects and similar ones deserve all the attention from the press and the Nobel prize committee that they have received.

What I am suggesting, however, is that there may be a risk for these fields, and physics in general, if these are the only physics-research updates and results that the public encounters.

Public POV

Just under a decade ago, a number of focus groups and surveys of the public’s attitudes towards science were commissioned by ScienceCounts, a not-for-profit outfit supported by the American Physical Society (APS), the American Association for the Advancement of Science (AAAS) and many other science organizations. The good news: people had a high regard for science in general, and scientists in particular. The bad news: only 25% of those surveyed believed that government funding of science research was necessary.

The alarming aspect of this study is that many people could not readily cite any personal benefit from government-funded scientific research. If the public and their elected representatives do not see how scientific research benefits their daily lives, then we risk the public deciding that the appropriate science funding level should be comparable to public arts funding.

Between the Higgs boson and the Big Bang, between the subatomic and astrophysical scales, lies another regime – the human scale – where all of us, and in particular the taxpayers who help fund our research, reside

The elucidation and comprehension of the laws of nature that govern the universe, and account for how it originated and continues to evolve, is truly one of the greatest accomplishments of humankind. Similarly, the identification of the quantum of excitation of the Higgs’ field and the development and confirmation of the Standard Model of particle physics is a monumental advance in our understanding of the world. But between the Higgs boson and the Big Bang, between the subatomic and astrophysical scales, lies another regime – the human scale – where all of us, and in particular the taxpayers who help fund our research, reside.

To be sure, research in particle physics and astrophysics has led to substantial technological applications – from the development of the World Wide Web and medical imaging to GPS navigation and satellite communications. These have had a great impact on society, but the applications were not the goals of this research. The main goal of condensed-matter research, on the other hand, is to understand the fundamental principles underlying the properties and behaviours of materials, so that these properties may be controlled and manipulated for desired ends.Potential uses Ferrofluid on a reflective glass plate, with a rare-earth magnet underneath. Rare-earth magnets could improve the effectiveness of wind turbines and jet engines. (CC BY SA 3.0 Gregory F Maxwell)

A central motivation behind the study of thermoelectric materials – solid-state semiconductors that transform heat into electric power or produce cold from an applied voltage – for example, is to be able to fabricate devices with improved efficiency and practical use. Similarly, there is much interest in rare-earth magnets, which could improve the effectiveness of wind turbines (used as permanent magnet-generator systems) and jet engines. Many laboratories, using different approaches, are working to develop a quantum computer but all of them employ solid-state devices as the basis of their qubits.

The success of condensed-matter physics teaches us that to understand the world around us we cannot rely solely on the techniques of particle physics or astrophysics. As Nobel-prize-winning physicist Philip Anderson explained in his excellent 1972 essay “More is different” (Science 177 393), simply knowing the properties and interactions of fundamental particles (and even, I would add, the mechanisms by which stars, planets and galaxies form and evolve) is insufficient to understanding physics on the human scale. As Anderson put it, “there are more levels of organization between human ethology [the study of behaviour and social organization] and DNA than there are between DNA and quantum electrodynamics, and each level can require a whole new conceptual structure.”

Attention-grabbing science

In the early part of the 20th century, the development of quantum mechanics meant that we could get a better understanding of the electronic properties of solids – whether they are metals, insulators or semiconductors. The macroscopic properties of solid-state systems could be understood through the behaviour of individual electrons, yielding transformative devices such as the transistor and the light-emitting diode.

By the second half of the last century, phenomena such as magnetism and superconductivity were recognized as manifestations of emergent collective behaviours, arising from interactions between electrons. The role of interactions is central to understanding these so-called “quantum materials”, perfectly illustrating Anderson’s thesis. Nothing in the Standard Model can account for superconductivity or magnetism, nor how these two phenomena can coexist in iron pnictides materials.

Similarly, interactions between individual particles can yield fascinating phenomena in soft-condensed-matter systems such as sandpiles (Am J. Phys. 73 8). Here, the only relevant forces are gravity and friction, yet granular media can exhibit properties that appear counterintuitive. For example, while most materials become denser under pressure, sand can become less dense, which is why your footprints on wet sand will appear dry.Grains of truth Axial segregation demonstrated with a 50/50 mixture of uncooked rice and split peas. Studies of granular media are not merely academic, as the storage and transport of powders and grains is fundamental to the pharmaceutical, construction and agricultural industries. (Courtesy: James Kakalios/University of Minnesota. Reproduced from American Journal of Physics 73 8, with the permission of the American Association of Physics Teachers)

Another interesting phenomenon is that when a mixture of large and small sand particles is rotated about the long axis of a horizontal cylinder, the mixture will segregate into alternating bands of large and small sand particles like rings on a finger – a phenomenon termed “axial segregation”. The width of each band is much larger than the diameter of each sand grain and is a striking illustration of how local interactions can give rise to macroscopic ordering.

I feel that my father (who was a taxi driver) would have been interested to learn that the same physics that governs axial segregation also accounts for the spontaneous formation of traffic jams, as a fundamental instability of highway flow. Studies of granular media are not merely academic, as the storage and transport of powders and grains is fundamental to the pharmaceutical, construction and agricultural industries.

I concede that in capturing the public’s attention, astrophysics and particle physics have an important competitive advantage – the tools and fruits of their research generate striking visual images that readily spark one’s interest. Personally, I never tire of viewing photos from the Hubble, James Webb or other space-based telescopes. Images of the detectors at the LHC are similarly remarkable – in particular because they demonstrate that humanity is able to build machines of such scale and complexity, and moreover that these machines work.

Back in early July someone on Twitter (now referred to as X) posted an image of the Cathedral of Santa Maria del Fiore cathedral in Florence, Italy, and asked whether “humanity would ever produce something like this again?” I assumed that by “something” the poster meant “of similar scale and grandeur”. Consequently, I replied: “Good news – we have!” and embedded an image of the ATLAS detector at the LHC. But when it comes to condensed-matter physics, however, an image of a micro-computer – which to a large extent enables the research advances in astrophysics and high energy physics – would be a picture of a literal black box.

Materials matter

So what advice would I give to my colleagues in condensed-matter and materials-science research who wish to engage the public with our field? One advantage we have is that the results of our research are readily apparent to the public. From the moment we awake to the close of the day, people around the world are surrounded by the materials and products of our research.

This point is ably exploited by Mark Miodownik, a professor of materials and society at University College London in his 2014 popular science book Stuff Matters: Exploring the Marvellous Materials that Shape our Man-Made World. The prize-winning book is one of the few popular-science books that highlights materials research, and was Physics World‘s 2014 Book of the Year. In it, Miodownik uses the framing device of a photograph of himself siting at a table on his rooftop, drinking a cup of tea. Each chapter then discusses the history and science behind a material present in this photo – steel, glass, porcelain, paper and plastic.

In his 2019 follow-up popular science book, Liquid: the Delightful and Dangerous Substances that Flow Through our Lives, Miodownik describes the fascinating science of fluids. This time, each chapter focuses on a liquid he encounters while on a transatlantic flight from the UK to the US – from the contents of the drinks cart to the jet fuel, from liquid soap in the toilets to the ink in ballpoint pens.Similar but different The molecules CH4 and CF4 are structurally and electronically similar, but when linked into long-chain polymers the former yields petroleum (left) while the latter produces Teflon (right) – both useful materials, for very different reasons. (Courtesy: CC0 Nefronus; iStock/Wirestock)

Other books – including physicists Sidney Perkowitz’s book Universal Foam: From Cappuccino to the Cosmos and Diandra Leslie-Pelecky’s The Physics of NASCAR: How to Make Steel + Gas + Rubber = Speed; as well as websites such as Nanoscale Views and FunSize Physics – also bring home the implicit message that we are surrounded by materials physics. Whether the interacting elements are electrons, macroscopic grains of sand or mesoscopic structures – the molecules CH4 and CF4 are structurally and electronically similar, but when linked into long-chain polymers the former yields petroleum while the latter produces Teflon (MRS Bulletin 37 1079) – Anderson’s argument that “more is different” holds.

Universal and relatable

Concepts from condensed-matter physics have been applied to situations that nearly anyone can relate to. A recent paper by Pablo Gottheil of Leipzig University and colleagues connects the physics of jamming of granular systems to the conditions under which cancer cells can metastasize and move away from their tumour of origin to other parts of the body (Phys. Rev. X 13 031003). While one must, of course, avoid over-promising, one can legitimately argue that fundamental research in disordered materials can be both inspiring and practical.

The very nature of big-science projects such as the LHC, LIGO and the JWST requires many scientists and engineers working together to address particular research goals – be it observing the Higgs boson or determining whether gravitational waves exist. In contrast, advances in condensed-matter physics usually take place with many scientists working mostly independently on a broad range of research problems. Some of these studies require large facilities such as high-magnetic field labs or neutron scattering sources – but the collaborations in condensed-matter physics are orders of magnitude smaller than in particle physics. This enables a nimbleness and flexibility that our field has exploited to great benefit.

Ultimately, as scientists, we study the subjects we do because they interest us – we should share that interest with others. Science communication need not involve the very latest research advances. For example, whenever I give a public lecture, I try to find a reason to show scanning tunnelling micrographs (STM), as most of the audience is unaware that we can routinely image surfaces with atomic-level resolution. I then point out that the same physics underlying an STM also operates in the tunnelling diodes and other devices found in their smart phones and computers.

As the television networks used to say when promoting a series of reruns: if you haven’t seen it before, it’s new to you. To my fellow condensed-matter and materials science colleagues, I encourage each of you to share your research far and wide, and engage with the public as often as you can. As the transistor demonstrates, little things can have a big impact on all of our lives.

James Kakalios is the Taylor Distinguished Professor in the School of Physics and Astronomy at the University of Minnesota and the author of several popular science books, including The Physics of Everyday Things.

FROM PHYSICSWORLD.COM    10/8/2023