Tag Archives: quasicrystals

Wormlike communication at the nanoscale

These days I need a little joy and these two researchers seem happy to share,

Prof. Dirk Grundler and doctoral assistant Sho Watanabe with a broadband spin-wave spectroscopy set up. Credit: EPFL / Alain Herzog

A July 15, 2020 news item on phys.org announces the development that so delights these researchers,

Researchers at EPFL [École polytechnique fédérale de Lausanne; Switzerland] have shown that electromagnetic waves coupled to precisely engineered structures known as artificial ferromagnetic quasicrystals allow for more efficient information transmission and processing at the nanoscale. Their research also represents the first practical demonstration of Conway worms, a theoretical concept for the description of quasicrystals.

A July 15, 2020 EPFL press release, which originated the news item, explains further,

High-frequency electromagnetic waves are used to transmit and process information in microelectronic devices such as smartphones. It’s already appreciated that these waves can be compressed using magnetic oscillations known as spin waves or magnons. This compression could pave the way for the design of nanoscale, multifunctional microwave devices with a considerably reduced footprint. But first, scientists need to gain a better understanding of spin waves – or precisely how magnons behave and propagate in different structures.

Learning more about aperiodic structures

In a study conducted by the doctoral assistant Sho Watanabe, postdoctoral researcher Dr. Vinayak Bhat, and further team members, the scientists from EPFL’s Laboratory of Nanoscale Magnetic Materials and Magnonics (LMGN) examined how electromagnetic waves propagate, and how they could be manipulated, in precisely engineered nanostructures known as artificial ferromagnetic quasicrystals. The quasicrystals have a unique property: their structure is aperiodic, meaning that their constituent atoms or tailor-made elements do not follow a regular, repeating pattern but are still arranged deterministically. Although this characteristic makes materials especially useful for the design of everyday and high-tech devices, it remains poorly understood.

Faster, easier transmission of information

The LMGN team found that, under controlled conditions, a single electromagnetic wave coupled to an artificial quasicrystal splits into several spin waves, which then propagate within the structure. Each of these spin waves represents a different phase of the original electromagnetic wave, carrying different information. “It’s a very interesting discovery, because existing information-transmission methods follow the same principle,” says Dirk Grundler, an associate professor at EPFL’s School of Engineering (STI). “Except you need an extra device, a multiplexer, to split the input signal because – unlike in our study – it doesn’t divide on its own.”

Grundler also explains that, in conventional systems, the information contained in each wave can only be read at different frequencies – another inconvenience that the EPFL team overcame in their study. “In our two-dimensional quasicrystals, all the waves can be read at the same frequency,” he adds. The findings have been published in the journal Advanced Functional Materials.

Waves that spread like worms

The researchers also observed that, rather than propagating randomly, the waves often moved like so-called Conway worms, named after a well-known mathematician John Horton Conway who also developed a model to describe the behavior and feeding patterns of prehistoric worms. Conway discovered that, within two-dimensional quasicrystals, constituent elements arrange like meandering worms following a Fibonacci sequence. Thereby they form selected one-dimensional quasicrystals. “Our study represents the first practical demonstration of this theoretical concept, proving that the sequences induce interesting functional properties of waves in a quasicrystal,” says Grundler.

Take a look at that last paragraph. A mathematician develops a model for how prehistoric worms may have moved and applies it, theoretically, to 2D quasicrystals which these researchers believe they’ve observed in the laboratory and they believe this may have an impact on our future electronic devices. Sometimes I sit at home in wonder.

Here’s a link to and a citation for the paper,

Direct Observation of Worm‐Like Nanochannels and Emergent Magnon Motifs in Artificial Ferromagnetic Quasicrystals by Sho Watanabe, Vinayak S. Bhat, Korbinian Baumgaert, Dirk Grundler. Advanced Functional Materials DOI: https://doi.org/10.1002/adfm.202001388 First published: 15 July 2020

This is an open access paper.

The mention of quasicrystals reminded me of Daniel Schechtman who received the Nobel Prize for Chemistry in 2011 and who was mentioned in a December 24, 2013 posting here,

“I suggested earlier that this achievement has a fabulous quality and the Daniel Schechtman backstory is the reason. The winner of the 2011 Nobel Prize for Chemistry, Schechtman was reviled for years [emphasis mine] within his scientific community as Ian Sample notes in his Oct. 5, 2011 article on the announcement of Schechtman’s Nobel win written for the Guardian newspaper (Note: A link has been removed),

A scientist whose work was so controversial he was ridiculed and asked to leave his research group has won the Nobel Prize in Chemistry.

Daniel Shechtman, 70, a researcher at Technion-Israel Institute of Technology in Haifa, received the award for discovering seemingly impossible crystal structures in frozen gobbets of metal that resembled the beautiful patterns seen in Islamic mosaics.

Images of the metals showed their atoms were arranged in a way that broke well-establised rules of how crystals formed, a finding that fundamentally altered how chemists view solid matter.

You may want to click on the Guardian link to the full story about Schechtman and his quasicrystals. As for my December 24, 2013 posting, that features news of the creation of the first single-element quasicrystal in a laboratory along with an excerpt of the Schechtman story (scroll down about 50% of the way).

The latest ‘golden’ age for electronics

I don’t know the dates for the last ‘golden’ age of electronics but I can certainly understand why these Japanese researchers are excited about their work. In any event, I think the ‘golden age’ is more of a play on words. From a June 25, 2019 news item on Nanowerk (Note: A link has been removed),

One way that heat damages electronic equipment is it makes components expand at different rates, resulting in forces that cause micro-cracking and distortion. Plastic components and circuit boards are particularly prone to damage due to changes in volume during heating and cooling cycles. But if a material could be incorporated into the components that compensates for the expansion, the stresses would be reduced and their lifetime increased.

Everybody knows one material that behaves like this: liquid water expands when it freezes and ice contracts when it melts. But liquid water and electronics don’t mix well – instead, what’s needed is a solid with “negative thermal expansion” (NTE).

Although such materials have been known since the 1960s, a number of challenges had to be overcome before the concept would be broadly useful and commercially viable. In terms of both materials and function, these efforts have only had limited success.

The experimental materials had been produced under specialized laboratory conditions using expensive equipment; and even then, the temperature and pressure ranges in which they would exhibit NTE were well outside normal everyday conditions.

Moreover, the amount they expanded and contracted depended on the direction, which induced internal stresses that changed their structure, meaning that the NTE property would not last longer than a few heating and cooling cycles.

A research team led by Koshi Takenaka of Nagoya University has succeeded in overcoming these materials-engineering challenges (APL Materials, “Valence fluctuations and giant isotropic negative thermal expansion in Sm1–xRxS (R = Y, La, Ce, Pr, Nd)”).

A June 22, 2019 Nagoya University press release (also on EurekAlert but published on June 25, 2019), which originated the news item, provides more technical detail,

Inspired by the series of work by Noriaki Sato, also of Nagoya University – whose discovery last year of superconductivity in quasicrystals was considered one of the top ten physics discoveries of the year by Physics World magazine – Professor Takenaka took the rare earth element samarium and its sulfide, samarium monosulfide (SmS), which is known to change phase from the “black phase” to the smaller-volume “golden phase”. The problem was to tune the range of temperatures at which the phase transition occurs. The team’s solution was to replace a small proportion of samarium atoms with another rare earth element, giving Sm1-xRxS, where “R” is any one of the rare earth elements cerium (Ce), neodymium (Nd), praseodymium (Pr) or yttrium (Y). The fraction x the team used was typically 0.2, except for yttrium. These materials showed “giant negative thermal expansion” of up to 8% at ordinary room pressure and a useful range of temperatures (around 150 degrees) including at room temperature and above … . Cerium is the star candidate here because it is relatively cheap.

The nature of the phase transition is such that the materials can be powdered into very small crystal sizes around a micron on a side without losing their negative expansion property. This broadens the industrial applications, particularly within electronics.

While the Nagoya University group’s engineering achievement is impressive, how the negative expansion works is fascinating from a fundamental physics viewpoint. During the black-golden transition, the crystal structure stays the same but the atoms get closer together: the unit cell size becomes smaller because (as is very likely but perhaps not yet 100% certain) the electron structure of the samarium atoms changes and makes them smaller – a process of intra-atomic charge transfer called a “valence transition” or “valence fluctuation” within the samarium atoms … . “My impression,” says Professor Takenaka, “is that the correlation between the lattice volume and the electron structure of samarium is experimentally verified for this class of sulfides.”

More specifically, in the black (lower temperature) phase, the electron configuration of the samarium atoms is (4f)6, meaning that in their outermost shell they have 6 electrons in the f orbitals (with s, p and d orbitals filled); while in the golden phase the electronic configuration is (4f)5(5d)1 -an electron has moved out of a 4f orbital into a 5d orbital. Although a “higher” shell is starting to be occupied, it turns out – through a quirk of the Pauli Exclusion Principle – that the second case gives a smaller atom size, leading to a smaller crystal size and negative expansion.

But this is only part of the fundamental picture. In the black phase, samarium sulfide and its doped offshoots are insulators – they do not conduct electricity; while in the golden phase they turn into conductors (i.e. metals). This is suggesting that during the black-golden phase transition the band structure of the whole crystal is influencing the valance transition within the samarium atoms. Although nobody has done the theoretical calculations for the doped samarium sulfides made by Professor Takenaka’s group, a previous theoretical study has indicated that when electrons leave the samarium atoms’ f orbital, they leave behind a positively charged “hole” which itself interacts repulsively with holes in the crystal’s conduction band, affecting their exchange interaction. This becomes a cooperative effect that then drives the valence transition in the samarium atoms. The exact mechanism, though, is not well understood.

Nevertheless, the Nagoya University-led group’s achievement is one of engineering, not pure physics. “What is important for many engineers is the ability to use the material to reduce device failure due to thermal expansion,” explains Professor Takenaka. “In short, in a certain temperature range – the temperature range in which the intended device operates, typically an interval of dozens of degrees or more – the volume needs to gradually decrease with a rise in temperature and increase as the temperature falls. Of course, I also know that volume expansion on cooling during a phase transition [like water freezing] is a common case for many materials. However, if the volume changes in a very narrow temperature range, there is no engineering value. The present achievement is the result of material engineering, not pure physics.”

Perhaps it even heralds a new “golden” age for electronics.

I worked in a company for a data communications company that produced hardware and network management software. From a hardware perspective, heat was an enemy which distorted your circuit boards and cost you significant money not only for replacements but also when you included fans to keep the equipment cool (or as cool as possible).

Enough with the reminiscences, here’s a link to and a citation for the paper,

Valence fluctuations and giant isotropic negative thermal expansion in Sm1–xRxS (R = Y, La, Ce, Pr, Nd) by D. Asai, Y. Mizuno, H. Hasegawa, Y. Yokoyama, Y. Okamoto, N. Katayama, H. S. Suzuki, Y. Imanaka, and K. Takenaka. Applied Physics Letters > Volume 114, Issue 14 > 10.1063/1.5090546 or Appl. Phys. Lett. 114, 141902 (2019); https://doi.org/10.1063/1.5090546. Published Online: 12 April 2019

This paper is behind a paywall.

INVESTING IN CANADA’S FUTURE; Strengthening the Foundations of Canadian Research (Review of fundamental research final report): 2 of 3

This is the middle commentary on the report titled,(INVESTING IN CANADA’S FUTURE; Strengthening the Foundations of Canadian Research). Part 1 of my commentary having provided some introductory material and first thoughts about the report, this part offers more detailed thoughts and Part 3 offers ‘special cases’ and sums up some of the ideas first introduced in part 1.

The report: the good, the informative, and the problematic

As Canadian government reports go, this is quite readable and I’m delighted to note some sections are downright engaging. (Thank you to the writer)

Happily, the report acknowledges the problems with the usual measures for research performance (p. xiv print; p. 18 PDF in the Executive Summary and, also, in Chapter 3). Also happily, the panel describes how the scope of the disciplines was decided,

Among the early challenges for the Panel were misinterpretation of its moniker and the related scope of its work. The term “fundamental science” originated with federal Budget 2016, which announced the Government of Canada’s intent to undertake a review.3 Alignment of terminology followed. Some members of the anglophone research community were understandably concerned that the Panel’s mandate excluded applied science in a range of fields, as well as the social sciences and humanities. Francophone researchers, accustomed to les sciences sociales et humaines, were more sanguine.

Minister Duncan [Kirsty Duncan], whose own scholarship cuts across the natural sciences, social sciences, and humanities, made it clear from the outset that the Panel was to examine the full range of scientific and scholarly disciplines. The Panel’s secretariat and members similarly emphasized the breadth of our review. We were accordingly delighted to receive submissions from many researchers and organizations representative of disciplines supported by the three granting councils, others doing transdisciplinary research who sometimes find themselves in limbo, and others again frustrated that the lack of collaboration across the councils has effectively shut out their disciplines altogether.

A residual source of some confusion was the term “fundamental”, which is used infrequently in the social sciences and humanities even though much scholarship in those fields is arguably basic or conceptual.

The Panel again took a pragmatic view. Our mandate was derived in meaningful measure from concerns that Canada’s capacity for generation of exciting new knowledge had been eroded. We therefore assumed our remit ranged from basic science focused on making major discoveries to applied science with important technological implications, and from deep philosophical inquiry to rigorous economic evaluations of policies and programs.

The Panel emphasizes in this latter regard that societies without great science and scholarship across a wide range of disciplines are impoverished in multiple dimensions. From the social sciences and humanities, contributions range from deeper understanding of the complexity of human nature and social structures to grace in self-expression and excellence and beauty in the creative and performing arts. From the natural and health sciences and engineering, while attention often focuses on practical applications, basic research provides the breakthrough insights that fundamentally change our understanding of the natural world and our cosmos. We return to this subject in Chapter 2.

The Panel also observes that these categorizations are all focused on research subject matter, when in fact the subject that really matters may be the person doing the research. Postsecondary education enriched by exposure to basic research provides citizens with an outlook and intellectual tools that are extraordinarily well-suited to technological and social innovation. Indeed, countless authors of abstract graduate theses have gone on to lives of deep and productive engagement with practical problems, bringing with them perspectives that reflect an inquiring and critical mind.

In brief, the Panel’s primary interest is in the extramural research realm, and particularly in supports for research into topics chosen by scholars and scientists from the full range of disciplines, using methods that they have developed or adapted, and subject to review by research colleagues. This research may be basic or applied. It may be project-based or programmatic. And it may have early application or no immediate relevance. However, a key criterion is that the work is sufficiently excellent to withstand critical scrutiny by peers, [emphasis mine] and produces knowledge that, after appropriate review, can be shared widely to advance the collective store of knowledge and ideas in the relevant field or fields. (p. 4-5 print; pp. 38-9 PDF)

Here’s a problem not mentioned in the report. Sometimes, the most exciting work is not appreciated or even approved by your peers. Daniel Schechtman’s work with quasicrystals  illustrates the issue (from the Dan Schechtman Wikipedia entry),

“I was a subject of ridicule and lectures about the basics of crystallography. The leader of the opposition to my findings was the two-time Nobel Laureate Linus Pauling, [emphasis mine] the idol of the American Chemical Society and one of the most famous scientists in the world. For years, ’til his last day, he fought against quasi-periodicity in crystals. He was wrong, and after a while, I enjoyed every moment of this scientific battle, knowing that he was wrong.”[citation needed]

Linus Pauling is noted saying “There is no such thing as quasicrystals, only quasi-scientists.”[15] Pauling was apparently unaware of a paper in 1981 by H. Kleinert and K. Maki which had pointed out the possibility of a non-periodic Icosahedral Phase in quasicrystals[16] (see the historical notes). The head of Shechtman’s research group told him to “go back and read the textbook” and a couple of days later “asked him to leave for ‘bringing disgrace’ on the team.”[17] [emphasis mine] Shechtman felt dejected.[15] On publication of his paper, other scientists began to confirm and accept empirical findings of the existence of quasicrystals.[18][19]

Schechtman does get back into the lab, finds support for his discovery from other scientists, and wins the Nobel Prize for Chemisty in 2011. But, that first few years was pretty rough sledding. As for the problem, how can you tell the difference between ground-breaking research and a ‘nutbar’ theory?

Getting back to the report, there’s a very nice listing of research milestones (the inception of various funding agencies, science ministries, important reports, and more) in the Canadian research landscape on pp. 8-9 print; pp. 42-3 PDF. The list stretches from 1916 to 2016. Oddly, the 2011 Jenkins report (also known as the Review of Federal Support to R&D report) is not on the list. Of course, it was a report commissioned by the then Conservative federal government.

Chapter 2 is the ‘Case for Science and Inquiry’ and it includes a bit of a history of the world, geologically speaking (p. 18 print; p. 52 PDF), and more. The scholars that are referenced tend to be from Europe and the US (sigh … isn’t there a way to broaden our perspectives?).

I was surprised that they didn’t include Wilder Penfield’s work in their partial listing of Canadian discoveries, and achievements in natural sciences, engineering, and health (p. 22 print; p. 56 PDF). From the Wilder Penfield Wikipedia entry*,

Wilder Graves Penfield OM CC CMG FRS[1] (January 26, 1891 – April 5, 1976) was an American-Canadian pioneering neurosurgeon once dubbed “the greatest living Canadian.”[2] He expanded brain surgery’s methods and techniques, including mapping the functions of various regions of the brain such as the cortical homunculus. His scientific contributions on neural stimulation expand across a variety of topics including hallucinations, illusions, and déjà vu. Penfield devoted a lot of his thinking to mental processes, including contemplation of whether there was any scientific basis for the existence of the human soul.[2]

Also mildly surprising was Ursula Franklin’s exclusion from their sampling of great Canadian thinkers in the social science and humanities (p. 23 print; p. 57 PDF) especially as there seems to be room for one more entry. From the Ursula Franklin Wikipedia entry,

Ursula Martius Franklin, CC OOnt FRSC (16 September 1921 – 22 July 2016), was a German-Canadian metallurgist, research physicist, author, and educator who taught at the University of Toronto for more than 40 years.[1] …

Franklin is best known for her writings on the political and social effects of technology. For her, technology was much more than machines, gadgets or electronic transmitters. It was a comprehensive system that includes methods, procedures, organization, “and most of all, a mindset”.[5] …

For some, Franklin belongs in the intellectual tradition of Harold Innis and Jacques Ellul who warn about technology’s tendency to suppress freedom and endanger civilization.[8] …

As noted earlier, Chapter 3 offers information about typical measures for scientific impact. There were two I didn’t mention. First, there are the scores for interprovincial collaboration. While we definitely could improve our international collaboration efforts, it’s the interprovincial efforts that tend to be pitiful (Note: I’ve had to create the table myself so it’s not identical to the report table’s format),

Province or Territory  Collaborative rates 2003-2014
Interprovincial International
Alberta 24.4 42.5
British Columbia 23.0 48.2
Manitoba 33.5 39.7
New Brunswick 35.7 38.0
Newfoundland and Labrador 33.6 38.7
Northwest Territories 86.9 32.5
Nova Scotia 34.7 40.9
Nunavut 85.7 34.5
Ontario 14.8 43.4
Prince Edward island 46.7 40.6
Québec 16.9 43.8
Saskatchewan 33.9 41.7
Yukon 79.4 39.0
Canada 9.8 43.7

* *The interprovincial collaboration rates (IPC) are computed on whole counts, not fractional counts. So, for example, a publication with authors from four provinces would count as one for Canada and one for each of the provinces. So the IPC for the whole of Canada would be 1 out of 874,475 (Canada’s whole publication count over 2003–2014) and the IPC for Ontario (for example) would be 1 out of 396,811 (the whole count for Ontario). Therefore the interprovincial collaboration rate would be lower for Canada than for Ontario. (p. 39 print; 73 PDF)

Second, there are the prizes,

Moving from highly-cited researchers and papers to the realm of major international research prizes takes us further into the realm of outlying talent. Major international prizes for research are relevant measures because they bring great prestige not just to individuals and teams, but also to institutions and nations. They are also the culmination of years of excellence in research and, particularly when prizes are won repeatedly across a range of disciplines, they send strong signals to the world about the health of a nation’s basic research ecosystem.

Unfortunately, Canada’s performance in winning international prizes is also lagging. In 2013 the Right Honourable David Johnston, Governor General of Canada, and Dr Howard Alper, then chair of the national Science, Technology and Innovation Council (STIC), observed that Canadians underperform “when it comes to the world’s most distinguished awards”, e.g., Nobel Prize, Wolf Prize, and Fields Medal. They added: “In the period from 1941 to 2008, Canadians received 19 of the top international awards in science—an impressive achievement, to be sure, but lacking when compared with the United States (with 1,403 winners), the United Kingdom (222), France (91), Germany (75) and Australia (42).”22 ix

There is an interesting wrinkle to the dominance of the U.S. in Nobel prizes.23 Over 30 per cent of all U.S. Nobel laureates since 1950 were foreign-born, with that proportion rising over time. From 2007 to 2016, the 54 Nobel prizes awarded to U.S.-based researchers included 20 immigrants. Sources differ as to whether more of the U.S. Nobel laureates originated from Canada or Germany, but the best estimate is that, since 1901, there have been 15 Canadian-born, and in many cases Canadian-educated, Nobel laureates based in the U.S.—double the total number of Nobel prizes awarded to Canadian-based researchers in the same period.

From the standpoint of international recognition, 2015 was an exceptional year. Canadians won two of the pinnacle awards: a Nobel prize (Arthur McDonald for Physics) and a Wolf prize (James Arthur for Mathematics). Those prizes celebrate work that exemplifies two very different models of discovery. As a theoretical mathematician, Dr Arthur’s pioneering papers in automorphic forms have been overwhelmingly sole-authored; his long-term support has come from modest NSERC Discovery Grants. As a particle physicist, Dr McDonald has led a large team in developing and operating the renowned Sudbury Neutrino Laboratory, a major science facility purpose-built deep in an active nickel mine, where startling observations have been made that are forcing a reconsideration of The Standard Model for Elementary Particles. In both cases, however, what matters is that the work began decades ago, and Canada provided long-term support at the levels and in forms required to enable path-breaking discoveries to be made.

Canada cannot assume that there will be a series of other pinnacle prizes awarded based on discoveries that tap into work initiated in the 1970s and 1980s. To ensure a continuous pipeline of successful nominations for international awards, research institutions must be supported consistently to recruit and retain outstanding scholars and scientists. They in turn must be supported to create world-class research environments through meritocratic adjudication processes that offer fair access to appropriate levels of consistent funding for scientific inquiry. Our assessment thus far has not given us great confidence that these winning conditions are being created, let alone enhanced. (pp. 46-7 print; pp. 80-1 PDF)

I found one more interesting bit in the report, a dated list of Canadian science advice vehicles. Somewhat optimistically given the speed with which the initiative has moved forward, they’ve listed a Canadian chief science advisor for 2017 (p. 54 print; p. 88 PDF). Understandably, since it is a recommendation, they left out the NACRI, .

Again, here’s a link to the other parts:

INVESTING IN CANADA’S FUTURE; Strengthening the Foundations of Canadian Research (Review of fundamental research final report) Commentaries

Part 1

Part 3

*’enty’ corrected to ‘entry’ and a link to Wilder Penfield’s Wikipedia entry was added on June 15, 2017.

A method for producing two-dimensional quasicrystals from metal organic networks

A July 13, 2016 news item on ScienceDaily highlights an advance where quasicrystals are concerned,

Unlike classical crystals, quasicrystals do not comprise periodic units, even though they do have a superordinate structure. The formation of the fascinating mosaics that they produce is barely understood. In the context of an international collaborative effort, researchers at the Technical University of Munich (TUM) have now presented a methodology that allows the production of two-dimensional quasicrystals from metal-organic networks, opening the door to the development of promising new materials.

A July 13, 2016 TUM press release (also on EurekAlert), which originated the news item, explains further,

Physicist Daniel Shechtman [emphasis mine] merely put down three question marks in his laboratory journal, when he saw the results of his latest experiment one day in 1982. He was looking at a crystalline pattern that was considered impossible at the time. According to the canonical tenet of the day, crystals always had so-called translational symmetry. They comprise a single basic unit, the so-called elemental cell, that is repeated in the exact same form in all spatial directions.

Although Shechtman’s pattern did contain global symmetry, the individual building blocks could not be mapped onto each other merely by translation. The first quasicrystal had been discovered. In spite of partially stark criticism by reputable colleagues, Shechtman stood fast by his new concept and thus revolutionized the scientific understanding of crystals and solid bodies. In 2011 he ultimately received the Nobel Prize in Chemistry. To this day, both the basic conditions and mechanisms by which these fascinating structures are formed remain largely shrouded in mystery.

A toolbox for quasicrystals

Now a group of scientists led by Wilhelm Auwärter and Johannes Barth, both professors in the Department of Surface Physics at TU Munich, in collaboration with Hong Kong University of Science and Technology (HKUST, Prof. Nian Lin, et al) and the Spanish research institute IMDEA Nanoscience (Dr. David Écija), have developed a new basis for producing two-dimensional quasicrystals, which might bring them a good deal closer to understanding these peculiar patterns.

The TUM doctoral candidate José Ignacio Urgel made the pioneering measurements in the course of a research fellowship at HKUST. “We now have a new set of building blocks that we can use to assemble many different new quasicrystalline structures. This diversity allows us to investigate on how quasicrystals are formed,” explain the TUM physicists.

The researchers were successful in linking europium – a metal atom in the lanthanide series – with organic compounds, thereby constructing a two-dimensional quasicrystal that even has the potential to be extended into a three-dimensional quasicrystal. To date, scientists have managed to produce many periodic and in part highly complex structures from metal-organic networks, but never a quasicrystal.

The researchers were also able to thoroughly elucidate the new network geometry in unparalleled resolution using a scanning tunnelling microscope. They found a mosaic of four different basic elements comprising triangles and rectangles distributed irregularly on a substrate. Some of these basic elements assembled themselves to regular dodecagons that, however, cannot be mapped onto each other through parallel translation. The result is a complex pattern, a small work of art at the atomic level with dodecagonal symmetry.

Interesting optical and magnetic properties

In their future work, the researchers are planning to vary the interactions between the metal centers and the attached compounds using computer simulation and experiments in order to understand the conditions under which two-dimensional quasicrystals form. This insight could facilitate the future development of new tailored quasicrystalline layers.

These kinds of materials hold great promise. After all, the new metal-organic quasicrystalline networks may have properties that make them interesting in a wide variety of application. “We have discovered a new playing field on which we can not only investigate quasicrystallinity, but also create new functionalities, especially in the fields of optics and magnetism,” says Dr. David Écija of IMDEA Nanoscience.

For one, scientists could one day use the new methodology to create quasicrystalline coatings that influence photons in such a manner that they are transmitted better or that only certain wavelengths can pass through the material.

In addition, the interactions of the lanthanide building blocks in the new quasicrystals could facilitate the development of magnetic systems with very special properties, so-called “frustrated systems”. Here, the individual atoms in a crystalline grid interfere with each other in a manner that prevents grid points from achieving a minimal energy state. The result: exotic magnetic ground states that can be investigated as information stores for future quantum computers.

The researchers have made an image available,

The quasicrystalline network built up with europium atoms linked with para-quaterphenyl–dicarbonitrile on a gold surface (yellow) - Image: Carlos A. Palma / TUM

The quasicrystalline network built up with europium atoms linked with para-quaterphenyl–dicarbonitrile on a gold surface (yellow) – Image: Carlos A. Palma / TUM

Here’s a link to and a citation for the paper,

Quasicrystallinity expressed in two-dimensional coordination networks by José I. Urgel, David Écija, Guoqing Lyu, Ran Zhang, Carlos-Andres Palma, Willi Auwärter, Nian Lin, & Johannes V. Barth. Nature Chemistry 8, 657–662 (2016) doi:10.1038/nchem.2507 Published online 16 May 2016

This paper is behind a paywall.

For anyone interested in more about the Daniel Schechter story and how he was reviled for his discovery of quasicrystals, there’s more in my Dec. 24, 2013 posting (scroll down about 60% of the way).

Single-element quasicrystal created in laboratory for the first time

There’s a background story which gives this breakthrough a fabulous aspect but, first, here’s the research breakthrough from a Dec. 24, 2013 news item on Nanowerk (Note: A link has been removed),

A research group led by Assistant Professor Kazuki Nozawa and Professor Yasushi Ishii from the Department of Physics, Faculty of Science and Engineering, Chuo University, Chief Researcher Masahiko Shimoda from the National Institute for Materials Science (NIMS) and Professor An-Pang Tsai from the Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, succeeded for the first time in the world in fabricating a three-dimensional structure of a quasicrystal composed of a single element, through joint research with a group led by Dr. Hem Raj Sharma from the University of Liverpool, the United Kingdom.

The Dec. 2, 2013 National Institute for Materials Science (NIMS; Japan) press release, which originated the news item, describes quasicrystals and the reasons why this particular achievement is such a breakthrough,

Quasicrystals are substances discovered in 1984 by Dr. Dan Shechtman (who was awarded the Nobel Prize in Chemistry in 2011). [emphasis mine] To date, quasicrystals have been found in more than one hundred kinds of alloy, polymer and nanoparticle systems. However, a quasicrystal composed of a single element has not been found yet. Quasicrystals have a beautiful crystalline structure which is closely related to the golden ratio, called a quasiperiodic structure. This structure is made of a pentagonal or decagonal atomic arrangement that is not found in ordinary periodic crystals (see the reference illustrations). Due to the complexity of the crystalline structure and chemical composition, much about quasicrystals is still veiled in mystery, including the mechanism for stabilizing a quasiperiodic structure and the novel properties of this unique type of crystalline structure. For these reasons, efforts have been made for a long time in the quest for a chemically simple type of quasicrystal composed only of a single element. The joint research group has recently succeeded in growing a crystal of lead with a quasiperiodic structure which is modeled on the structure of a substrate quasicrystal, by vapor-depositing lead atoms on the quasicrystal substrate of an existing alloy made of silver (Ag), indium (In) and ytterbium (Yb). Success using this approach had been reported for fabricating a single-element quasiperiodic film consisting of a single atomic layer (two-dimensional structure), but there had been no successful case of fabricating a single-element quasiperiodic structure consisting of multiple atomic layers (three-dimensional structure). This recent success by the joint research group is a significant step forward toward achieving single-element quasicrystals. It is also expected to lead to advancement in various fields, such as finding properties unique to quasiperiodic structures that cannot be found in periodic crystals and elucidating the mechanism of stabilization of quasiperiodic structures.

Here’s an image illustrating the researchers’ achievement,

Illustrations of the deposition structure of lead. The Tsai cluster in the substrate quasicrystal which is near the surface of the substrate is cut at the point where it contacts the surface. While lead usually has a face-centered cubic structure, it is deposited on the quasicrystal substrate in a manner that it recovers Tsai clusters which are cut near the surface of the substrate. This indicates that a crystal of lead is grown with the same structure as the structure of the quasicrystal substrate. (Courtesy National Institute for Materials Science, Japan)

Illustrations of the deposition structure of lead. The Tsai cluster in the substrate quasicrystal which is near the surface of the substrate is cut at the point where it contacts the surface. While lead usually has a face-centered cubic structure, it is deposited on the quasicrystal substrate in a manner that it recovers Tsai clusters which are cut near the surface of the substrate. This indicates that a crystal of lead is grown with the same structure as the structure of the quasicrystal substrate. (Courtesy National Institute for Materials Science, Japan)

I suggested earlier that this achievement has a fabulous quality and the Daniel Schechtman backstory is the reason. The winner of the 2011 Nobel Prize for Chemistry, Schechtman was reviled for years within his scientific community as Ian Sample notes in his Oct. 5, 2011 article on the announcement of Schechtman’s Nobel win written for the Guardian newspaper (Note: A link has been removed),

A scientist whose work was so controversial he was ridiculed and asked to leave his research group has won the Nobel Prize in Chemistry.

Daniel Shechtman, 70, a researcher at Technion-Israel Institute of Technology in Haifa, received the award for discovering seemingly impossible crystal structures in frozen gobbets of metal that resembled the beautiful patterns seen in Islamic mosaics.

Images of the metals showed their atoms were arranged in a way that broke well-establised rules of how crystals formed, a finding that fundamentally altered how chemists view solid matter.

On the morning of 8 April 1982, Shechtman saw something quite different while gazing at electron microscope images of a rapidly cooled metal alloy. The atoms were packed in a pattern that could not be repeated. Shechtman said to himself in Hebrew, “Eyn chaya kazo,” which means “There can be no such creature.”

The bizarre structures are now known as “quasicrystals” and have been seen in a wide variety of materials. Their uneven structure means they do not have obvious cleavage planes, making them particularly hard.

In an interview this year with the Israeli newspaper, Haaretz, Shechtman said: “People just laughed at me.” He recalled how Linus Pauling, a colossus of science and a double Nobel laureate, mounted a frightening “crusade” against him. After telling Shechtman to go back and read a crystallography textbook, the head of his research group asked him to leave for “bringing disgrace” on the team. “I felt rejected,” Shachtman said.

It takes a lot to persevere when most, if not all, of your colleagues are mocking and rejecting your work so bravo to Schechtman! And,bravo to the Japan-UK project researchers who have persevered to help solve at least part of a complex problem requiring that our basic notions of matter be rethought.

I encourage you to read Sample’s article in its entirety as it is well written and I’ve excerpted only bits of the story as it relates to a point I’m making in this post, i.e., perseverance in the face of extreme resistance.