Tag Archives: diamond

Formation of a time (temporal) crystal

It’s a crystal arranged in time according to a March 8, 2017 University of Texas at Austin news release (also on EurekAlert), Note: Links have been removed,

Salt, snowflakes and diamonds are all crystals, meaning their atoms are arranged in 3-D patterns that repeat. Today scientists are reporting in the journal Nature on the creation of a phase of matter, dubbed a time crystal, in which atoms move in a pattern that repeats in time rather than in space.

The atoms in a time crystal never settle down into what’s known as thermal equilibrium, a state in which they all have the same amount of heat. It’s one of the first examples of a broad new class of matter, called nonequilibrium phases, that have been predicted but until now have remained out of reach. Like explorers stepping onto an uncharted continent, physicists are eager to explore this exotic new realm.

“This opens the door to a whole new world of nonequilibrium phases,” says Andrew Potter, an assistant professor of physics at The University of Texas at Austin. “We’ve taken these theoretical ideas that we’ve been poking around for the last couple of years and actually built it in the laboratory. Hopefully, this is just the first example of these, with many more to come.”

Some of these nonequilibrium phases of matter may prove useful for storing or transferring information in quantum computers.

Potter is part of the team led by researchers at the University of Maryland who successfully created the first time crystal from ions, or electrically charged atoms, of the element ytterbium. By applying just the right electrical field, the researchers levitated 10 of these ions above a surface like a magician’s assistant. Next, they whacked the atoms with a laser pulse, causing them to flip head over heels. Then they hit them again and again in a regular rhythm. That set up a pattern of flips that repeated in time.

Crucially, Potter noted, the pattern of atom flips repeated only half as fast as the laser pulses. This would be like pounding on a bunch of piano keys twice a second and notes coming out only once a second. This weird quantum behavior was a signature that he and his colleagues predicted, and helped confirm that the result was indeed a time crystal.

The team also consists of researchers at the National Institute of Standards and Technology, the University of California, Berkeley and Harvard University, in addition to the University of Maryland and UT Austin.

Frank Wilczek, a Nobel Prize-winning physicist at the Massachusetts Institute of Technology, was teaching a class about crystals in 2012 when he wondered whether a phase of matter could be created such that its atoms move in a pattern that repeats in time, rather than just in space.

Potter and his colleague Norman Yao at UC Berkeley created a recipe for building such a time crystal and developed ways to confirm that, once you had built such a crystal, it was in fact the real deal. That theoretical work was announced publically last August and then published in January in the journal Physical Review Letters.

A team led by Chris Monroe of the University of Maryland in College Park built a time crystal, and Potter and Yao helped confirm that it indeed had the properties they predicted. The team announced that breakthrough—constructing a working time crystal—last September and is publishing the full, peer-reviewed description today in Nature.

A team led by Mikhail Lukin at Harvard University created a second time crystal a month after the first team, in that case, from a diamond.

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

Observation of a discrete time crystal by J. Zhang, P. W. Hess, A. Kyprianidis, P. Becker, A. Lee, J. Smith, G. Pagano, I.-D. Potirniche, A. C. Potter, A. Vishwanath, N. Y. Yao, & C. Monroe. Nature 543, 217–220 (09 March 2017) doi:10.1038/nature21413 Published online 08 March 2017

This paper is behind a paywall.

Unraveling carbyne (one-dimensional carbon)

An international group of researchers has developed a technique for producing a record-breaking length of one-dimensional carbon (carbon chain) according to an April 4, 2016 news item on Nanowerk,

Elemental carbon appears in many different modifications, including diamond, fullerenes and graphene. Their unique structural, electronic, mechanical, transport and optical properties have a broad range of applications in physics, chemistry and materials science, including composite materials, nanoscale light emitting devices and energy harvesting materials. Within the “carbon family”, only carbyne, the truly one-dimensional form of carbon, has not yet been synthesized despite having been studied for more than 50 years. Its extreme instability in ambient conditions rendered the final experimental proof of its existence elusive.

An international collaboration of researchers now succeeded in developing a novel route for the bulk production of carbon chains composed of more than 6,400 carbon atoms by using thin double-walled carbon nanotubes as protective hosts for the chains.

An April 4, 2016 University of Vienna press release (also on EurekAlert) provides another perspective on the research,

Even in its elemental form, the high bond versatility of carbon allows for many different well-known materials, including diamond and graphite. A single layer of graphite, termed graphene, can then be rolled or folded into carbon nanotubes or fullerenes, respectively. To date, Nobel prizes have been awarded for both graphene (2010) and fullerenes (1996). Although the existence of carbyne, an infinitely long carbon chain, was proposed in 1885 by Adolf von Baeyer (Nobel laureate for his overall contributions in organic chemistry, 1905), scientists have not yet been able to synthesize this material. Von Baeyer even suggested that carbyne would remain elusive as its high reactivity would always lead to its immediate destruction. Nevertheless, carbon chains of increasing length have been successfully synthesized over the last 50 years, with a record of around 100 carbon atoms (2003). This record has now been broken by more than one order of magnitude, with the demonstration of micrometer length-scale chains.

The new record

Researchers from the University of Vienna, led by Thomas Pichler, have presented a novel approach to grow and stabilize carbon chains with a record length of 6,000 carbon atoms, improving the previous record by more than one order of magnitude. They use the confined space inside a double-walled carbon nanotube as a nano-reactor to grow ultra-long carbon chains on a bulk scale. In collaboration with the groups of Kazu Suenaga at the AIST Tsukuba [National Institute of Advanced Industrial Science and Technology] in Japan, Lukas Novotny at the ETH Zürich [Swiss Federal Institute of Technology] in Switzerland and Angel Rubio at the MPI [Max Planck Institute] Hamburg in Germany and UPV/EHU [University of the Basque Country] San Sebastian in Spain, the existence of the chains has been unambiguously confirmed by using a multitude of sophisticated, complementary methods. These are temperature dependent near- and far-field Raman spectroscopy with different lasers (for the investigation of electronic and vibrational properties), high resolution transmission electron spectroscopy (for the direct observation of carbyne inside the carbon nanotubes) and x-ray scattering (for the confirmation of bulk chain growth).

The researchers present their study in the latest edition of Nature Materials. “The direct experimental proof of confined ultra-long linear carbon chains, which are more than an order of magnitude longer than the longest proven chains so far, can be seen as a promising step towards the final goal of unraveling the “holy grail” of carbon allotropes, carbyne”, explains the lead author, Lei Shi.

Application potential

Carbyne is very stable inside double-walled carbon nanotubes. This property is crucial for its eventual application in future materials and devices. According to theoretical models, carbyne’s mechanical properties exceed all known materials, outperforming both graphene and diamond. Carbyne’s electrical properties suggest novel nanoelectronic applications in quantum spin transport and magnetic semiconductors.

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

Confined linear carbon chains as a route to bulk carbyne by Lei Shi, Philip Rohringer, Kazu Suenaga, Yoshiko Niimi, Jani Kotakoski, Jannik C. Meyer, Herwig Peterlik, Marius Wanko, Seymur Cahangirov, Angel Rubio, Zachary J. Lapin, Lukas Novotny, Paola Ayala, & Thomas Pichler. Nature Materials (2016) doi:10.1038/nmat4617 Published online 04 April 2016

This paper is behind a paywall.

But, there is this earlier and open access version on arXiv.org,

Confined linear carbon chains: A route to bulk carbyne
Lei Shi, Philip Rohringer, Kazu Suenaga, Yoshiko Niimi, Jani Kotakoski, Jannik C. Meyer, Herwig Peterlik, Paola Ayala, Thomas Pichler (Submitted on 17 Jul 2015 (v1), last revised 20 Jul 2015 (this version, v2))

Making diamonds at room temperature with a new carbon material

Scientists at North Carolina State University (NCSU) claim to have found a new phase for solid carbon which allows them to create diamond materials at room temperature. From a Nov. 30, 2015 news item on Nanowerk,

Researchers from North Carolina State University have discovered a new phase of solid carbon, called Q-carbon, which is distinct from the known phases of graphite and diamond. They have also developed a technique for using Q-carbon to make diamond-related structures at room temperature and at ambient atmospheric pressure in air.

Phases are distinct forms of the same material. Graphite is one of the solid phases of carbon; diamond is another.

“We’ve now created a third solid phase of carbon,” says Jay Narayan, the John C. Fan Distinguished Chair Professor of Materials Science and Engineering at NC State and lead author of three [?] papers describing the work. “The only place it may be found in the natural world would be possibly in the core of some planets.”

A Nov. 30, 2015 NCSU news release (also on EurekAlert), which originated the news item, describes some of the new material’s properties,

Q-carbon has some unusual characteristics. For one thing, it is ferromagnetic – which other solid forms of carbon are not. [definition from its Wikipedia entry: Ferromagnetism is the basic mechanism by which certain materials (such as iron) form permanent magnets, or are attracted to magnets.]

“We didn’t even think that was possible,” Narayan says.

In addition, Q-carbon is harder than diamond, and glows when exposed to even low levels of energy.

“Q-carbon’s strength and low work-function – its willingness to release electrons – make it very promising for developing new electronic display technologies,” Narayan says.

But Q-carbon can also be used to create a variety of single-crystal diamond objects. …

The news release describes the process for creating Q-carbon,

Researchers start with a substrate, such as such as sapphire, glass or a plastic polymer. The substrate is then coated with amorphous carbon – elemental carbon that, unlike graphite or diamond, does not have a regular, well-defined crystalline structure. The carbon is then hit with a single laser pulse lasting approximately 200 nanoseconds. During this pulse, the temperature of the carbon is raised to 4,000 Kelvin (or around 3,727 degrees Celsius) and then rapidly cooled. This operation takes place at one atmosphere – the same pressure as the surrounding air.

The end result is a film of Q-carbon, and researchers can control the process to make films between 20 nanometers and 500 nanometers thick.

By using different substrates and changing the duration of the laser pulse, the researchers can also control how quickly the carbon cools. By changing the rate of cooling, they are able to create diamond structures within the Q-carbon.

“We can create diamond nanoneedles or microneedles, nanodots, or large-area diamond films, with applications for drug delivery, industrial processes and for creating high-temperature switches and power electronics,” Narayan says. “These diamond objects have a single-crystalline structure, making them stronger than polycrystalline materials. And it is all done at room temperature and at ambient atmosphere – we’re basically using a laser like the ones used for laser eye surgery. So, not only does this allow us to develop new applications, but the process itself is relatively inexpensive.”

And, if researchers want to convert more of the Q-carbon to diamond, they can simply repeat the laser-pulse/cooling process.

If Q-carbon is harder than diamond, why would someone want to make diamond nanodots instead of Q-carbon ones? Because we still have a lot to learn about this new material.

“We can make Q-carbon films, and we’re learning its properties, but we are still in the early stages of understanding how to manipulate it,” Narayan says. “We know a lot about diamond, so we can make diamond nanodots. We don’t yet know how to make Q-carbon nanodots or microneedles. That’s something we’re working on.”

NC State has filed two provisional patents on the Q-carbon and diamond creation techniques.

While the news release mentions Narayan is the lead author of three papers about this work, only two papers are cited at the end of the news release.

Here are the links and citations,

Research Update: Direct conversion of amorphous carbon into diamond at ambient pressures and temperatures in air by Jagdish Narayan and Anagh Bhaumik. APL Mater. 3, 100702 (2015); http://dx.doi.org/10.1063/1.4932622 [Published Oct. 7, 2015]

Novel Phase of Carbon, Ferromagnetism and Conversion into Diamond by Jagdish Narayan and Anagh Bhaumik. Published online Nov. 30 [, 2015] in the Journal of Applied Physics  DOI: 10.1063/1.4936595

Both articles are open access.

Virtual lego used to simulate self-assembling crystal structures

The Jan. 17, 2013 news release on EurekAlert describes a ‘soft’ or virtual lego computer simulation developed at the University of Vienna (Austria),

In developing these novel self-assembling materials, postdoc Barbara Capone has focused on the design of organic and inorganic building blocks, which are robust and can be produced at large scale. Capone has put forward, together with her colleagues at the Universities of Vienna and Mainz, a completely new pathway for the construction of building blocks at the nanoscale.

The team of researchers has shown that so-called block copolymer stars – that means polymers that consist of two different blocks and they are chemically anchored on a common point – have a robust and flexible architecture and they possess the ability to self-assemble at different levels. At the single-molecule level, they first order as soft patchy colloids which serve then as “soft Lego” for the emergence of larger structures. At the next level of self-assembly, the colloids form complex crystal structures, such as diamond or cubic phases.

The spatial ordering in the crystals can be steered through the architecture of the “soft Lego” and opens up the possibility for the construction of new materials at the macroscopic scale with desired structure. In this way, crystals can be built that have applications in, e.g., photonics, acting as filters for light of certain frequencies or as light guides.

You can find illustrations of the ‘diamond’ and the ‘cube’ produced by Capone and her colleagues with the news release on EurekAlert or here at the University of Vienna’s media portal where you may be able to find more information if you can read German. Alternatively, you can read the research paper,

Telechelic Star Polymers as Self-Assembling Units from the Molecular to the Macroscopic Scale by Barbara Capone, Ivan Coluzza, Federica LoVerso, Christos N. Likos, and Ronald Blaak in Physical Review Letters 109 [issue no. 23], 238301 (2012) [5 pages]DOI:10.1103/PhysRevLett.109.238301

This article is behind a paywall.